I think there are a lot of other big threats to startup businesses. Not all startup businesses depend on user generated content. Startups that make software or other products that aren't used and/or contributed to by essentially anonymous internet users don't have much to fear from this.
On the contrary, there are lots of startup businesses on the content creation side of the equation that could benefit from this legislation due to the increased risk and difficulty of pirating and distributing copyrighted works.
I create original art. When I have to work on distributing, I'm hampered by copyright law. I don't benefit from it. It harms me. Directly.
I've seen artists have their work infringed by others working for large corporations, and their ability to have something done about it quashed by a corporation wielding copyright law (see, for example, Timbaland vs. tempest)
Addendum: it looks like someone (someones?) is going around in this thread blanketing it in votes in favor of stricter copyright. Slightly creepy.
Well it required quite a bit of internet support and hostile publicity for the case to move one bit. Which goes on to prove that the copyright laws by themselves weren't providing protection for Tempest.
On the contrary, there are lots of startup businesses on the content creation side of the equation that could benefit from this legislation due to the increased risk and difficulty of pirating and distributing copyrighted works.