Kickstarter and Indiegogo - can this work?

I am thinking about starting a campaing on Indiegogo, and it takes some work. I am wonering whether it makes sense, and how does it work. Kickstarter has around 820k daily visitors and Indiegogo is at around 420k. So there is that many people browsing these sites, with money in their pockets, going over these projects and wanting to give away their money for free. I know that these sites make 5% of so of the funds raised, so they make the money, people obviously want to raise free capital too, but is this really about close to millions people per day browsing these websites, in order to give away their money for free. Too good to be true / what is the catch, type of situation here. Do you have any experience with this?

Thanks.

The catch is that you need a great and innovative idea in order to convince people to give you their money.
And if you dont pass the threshhold, you wont receive a single cent.

No one is giving their money "for free".
They pledge to give money in return for a perk, which most often is an actual tangible product.
If the target amount is not reached, they don't pay anything.

You post is not very coherent, so I don't understand exactly what you're trying to ask.

These websites have hundreds of success stories, so they clearly work. There is no catch.
Create something awesome, and people will buy it!