There's hard data and historical data and there's theories from not very smart conspiracy theorists who think behind everything there's a conspiracy theory. Illuminati is a word many idiots use to describe the Boogie Man/NWO/Evil under one term.
If you look at historical data you actually find interesting things, interesting organizations and connections. But these facts won't give you complete answers or an absolute truth. That's why many of these conspiracy theorists prefer to just say "Illuminati is controlling us and is evil." without having a fucking clue what they're talking about or who they're talking about.
If you want hard facts, just go and research, including in the resources of the particular organizations - things they state themselves. Is interesting. You won't have an "oh dang, the Illuminati are evil and are destroying us" moment, but is quite educational.
Read on Bilderberg, Club of Rome, Trilateral, Templer Knights, The Knights of Malta/Order of Malta, Jesuit Order, Francmasonery, The Vatican, etc - look who are the members, in what positions they are in various institutions, where they appear during various events, their positions on various issues, etc. I didn't bother much with this, I'm not a fan of this stuff and I have better use for my time. But if you go and read actual facts for 1-2 days you find enough interesting things to make your time worthwhile. That's all I did. OF course, same information might make one person scream conspiracy and another person just see a pattern that he can put to use at a smaller scale in his life.
I mean just take the Vatican. An amazingly powerful "society" smaller than a city, within the city of an actual state (Italy). Now tell me there's no such thing as people with amazing power, having great saying in decisions that affect the entire human civilization. Happily I am not one of those people who think X or Y is just pure good or pure evil. I think Vatican, X and Y did both great things as well as horrible things. So does that make them good or evil? How do you decide this without being the top most person within that organization and seeing the big picture and understanding it best.
There are days when I'm a complete asshole with people around me and days when I'm all milk and honey. If I can't demand from myself to be milk and honey every second with every person, no matter how nice or horrible he or she is, how could I demand that from somebody who is at entirely different level and size and made from multiple persons?
Bad shit happening - does that mean that every secret or not so mainstream society out there is evil? That's a rather long shot isn't it? Yes, they have power and influence. That's obvious. Another thing that is obvious is powerful people, just like weak people, congregate and cooperate to meet their common goals. So if you have X, Y and Z in positions of power having a highly similar agenda, obviously they will work together. Google+Yahoo+Bing all have similar goals and have an interest/agenda to expand the reach of internet worldwide because it means more money. Orthodox+Catholic+Islamic+Budhist churches all have a goal in people believing in God and being nice with each other so they can work together in that direction even though the don't agree on other things. Rockefellers+whoever also have some goals and plans. And so on. Finally, if I have a site about HDTVs and you have a site about Blu-Ray players, we can cooperate and grow together because we have a common interest. So would that make us a secret society? I mean we don't go and yell out loud our cooperative marketing strategies, so does that make us a secret society?
Another aspect is blame. People like to blame. They blame the government, the church, their brother, their mother, their cat and their ISP. They really love it. So whenever a person doesn't get what he wants in an easy way, is much easier to blame somebody else than figure out what he has to do to get there. You can't be 100 Kg and at the same time be a ballerina. That's what people don't get. Pretty much everything you want in life produces an incompatibility with other things. That translates into sacrifice. Some people make that sacrifice to become what they want, some people don't and blame the others.
Look at the SEO world. Some people rank in SERPs and make big money, most don't. So those who don't rank go and cry about Google being evil and X and Y being allowed to do some bad shit SEO wise because they're big brands. Does it matter? Those people understood things you didn't and they went and made certain sacrifices and got out of their comfort zone. If you have $100/mo budget and somebody else has $1mil/mo budget for SEO, complaining about not being able to win against them is just retarded. What you're doing is complain instead of understanding that the world and everything functions by certain rules and you're just not using the laws of the universe to your advantage and instead are simply complaining the universe isn't kissing your ass.
I could understand and respect (not necessarily accept) the opinion of somebody I somehow magically know he's not lying about what he's telling me, somebody who researched various secret organizations for years and he tells me in a compacted version his conclusions. I can respect that person because he actually went and spent part of his life researching and he's taking the time to share with me his findings. I can not respect somebody who watches some retarded conspiracy theory videos on YouTube and screams Illuminaty, NWO and conspiracy theory about everything and complains about everything and blames everybody. I just can't.
At the end of the day, you can allow yourself to be consumed by partial information and disinformation, or not give a fuck and go do whatever you like to do. You're going to live for under 100 years and then die. Nothing and nobody is stopping you from having a beautiful life. I don't care how powerful these organizations are, they won't stop you from becoming a pilot if you love flying or from traveling the world if you love seeig places and meeting people, or from making lots of money if you like sports cars and yachts. There's potential for good and potential for evil in every person, you and me included. You can not directly turn a switch and make somebody else good or evil and even if you could you shouldn't because is not your business. What you can is work on yourself so you evolve in the direction you want. And if you feed the good or evil potential in yourself enough, at some point you will influence those around you because it is contagious.
Ghandi put it best - "You must e the change you wish to see in the world".