Why don't most web 2.0 startups use sophisticated algorithms?
Lack of knowledge/ability? To avoid infringing patents (even accidentally)? Most users won't care? Not important in the problem domain?
This is different from a startup such as Google where PageRank is major breakthrough that is made obvious to everyone. We don't see many startups like Google in web 2.0. It seems that web 2.0 is more about harvesting people power and less about sophisticated algorithms.
Yes, one could. Though it isn't the question you originally asked, and so you shouldn't be surprised when you don't get an answer to that question. The question you asked was "why aren't startups using sophisticated algorithms?" ;-)