1. If you already have the fans, it is easier then ever to get revenue from them.
2. If you have a product that people want, or could want, it's easier then ever to essentially presale your art and get the capital you need to build the thing.
These are not insignificant points. To do the sorts of things that Zach Braff, Amanda Palmer or the crew of the Veronica Mars movie or doing now would have been difficult 5 years ago and more or less impossible 10 years ago.
This is progress.
What it isn't is a way to bring new bodies into any particular art form. If you only have 100 true fans, launching a crowd funding campaign isn't going to magically jump that to 1,000.
3. The number of people who are willing to support you with cash is ALWAYS much smaller then the sum of total people who are casual fans of your work.
You should note how these relatively big names have a relatively small number of supporters. At this point about 90,000 people have put money into the Veronica Mars Kickstarter. If only 90,000 people actually see the movie then it is an unqualified disaster.
I see this mistake all the time with artists. They look at their raw numbers of email addresses, Facebook "friends", etc. and assume that their total audience is X. Then they assume that their paying audience is 50% of X. In reality it may only be 10% of X. Or 1% of X.
The gap between "hey I like you" and "hey, here's some money" is HUGE.
So there are really three things to keep in mind when using Kickstarter or any crowd funding source.
It leverages existing fans, it doesn't create new ones.
It's a great tool for preselling art that want to see made.
Only a small portion of your fans will participate, so set your expectations carefully.