People who invest in movies invest for the same reasons all of us invest in anything-- to make money.
Hollywood is a business, albeit one rooted in entertainment, but let's face it-- many artists are also just in it for the money.
I don't think our world view of "entertainment" is going to shift the way that YC suggested in it's call for action. I think most of us (unfortunately) are still going to want to watch movies like Transformers 3 at a $200 million budget than a $1million dollar indie flick.
So, once we've recognized that uprooting involves figuring out how to finance movie production instead of shifting the realm of entertainment (at least, for our generation, perhaps future generations will just want to watch WOW and starcraft online), then we're getting somewhere.
Unfortunately, figuring out a way to finance a film that costs tens or hundreds of millions to produce is a pretty tricky endeavor.
Still, it will be pretty awesome when Brad Pitt signs onto his first crowd-sourced flick =)