Actually you can be completelly untraceable. The key is not to be untraceable/invisible but to make the traces go to somebody who isn't you.
In order to do this you will at some point have to break the law
Doing what GreyWolf suggested AND using either a hacked WiFi or an internet cafe without security cameras will make you untraceable because the trace ends up with a dead end - in first case the owner of the WiFi AP, in second an internet cafe.
Obviously in this process you have to invent an alternate/made-up identity.
If however you need to be able to get your hands on money for example, things become a lot more complicated because getting the money is a massive risk - it produces a link between your alternate identity and the real identity. That is why the folks who are stealing money online and stuff either do money laundering where they loose a percentage of the money in order to be able to keep the rest, or they use so-called "mules" which are like the pawns on a chess board - expandable. In other words some poor folks who don't know much and are told by the big boss "go to the bank and cash this money and bring it to me".
Generally speaking the folks who make money online from illegal activities are in a way or another connected to organized crime. Because of that pretty much every aspect of covering their tracks is covered at every level.
If you think using proxies, TOR or "private/encripted" networks is safe, you are wrong. As a matter of fact all data traffic (GSM,GPRS,3G,WAN,etc) is being monitored 24/7 by at least the NSA and for most states by the intelligence services of those states - for more details see "spy files" on WikiLeaks (actually read the proposals/presentations). Not only they monitor all traffic but they also have the capacity to decrypt strong encriptions on the fly - the NSA has anounced publily in the past they can crack SSL-128 by bruteforce in 2 seconds flat. Besides that they also made public that any communication with encryption higher than SSL-4096 is automatically flagged.
Things do not stop here. For GSM (at least) it is possible to intercept all communication to and from a certain phone without having access to the carrier (phone company). There are devices the size of a 4U server that can handle up to 64 phone streams at the same time. This is possible because the GSM security can be easily cracked. Even worse, they can listen to a phone even if the phone is not in a call. So if you're in a room discussing secret stuff with some other noob and you have the phone on the table they can hear you and you wouldn't know it. For the smartphones they can even access the webcam and you wouldn't know it.
All this is public information. Imagine the shit they can do that they didn't made public. I remember years ago when CRT monitors were the standard that they had devices which allowed them to see what was on a CRT monitor from a wan in front of the building. The CRT as basically an electron canon and produced a strong magnetic field. This field they picked up from a significant distance (tens of meters) and cleaned up and made it into a clone (distorted though) of the image you had on your monitor. This was years ago.
There are also directional microphones, laser microphones (they point it at a window and hear what is being talked inside because the window wibrates from the sound waves inside the room), etc.
I'm not saying that it is impossible to communicate securely, I am just saying it is extremely hard if you have the NSA after you. Hence you better be at the same level with them to stand a chance.
Happily, I only have to remain undetected by Google lol. A much easier task.
yeah, sorry to break it to you but staying 110% untrackable is almost impossible...
While technology exists to stay anonymous, the biggest problem will be yourself... Connect once with the wrong proxy and you are detectable, if you really want to stay highly anonymous, use different internet cafes all the time and also only connect through highly anonymous proxies.
But then again might be that this proxy keeps logs, and if someone really wants to know your real ip they could be able to track it maybe, and once that happens your isp would give out your ip immediately (assuming you did something illegal)
You could also chain proxies etc to give it an extra layer of security, but always know, it's virtually impossible to be 110% undetectable, but it is very well possible to hide your ass pretty good (just not to be invisible
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