One problem with this approach is that Youtube's search just feels so bad (at least compared to what you expect out of Google) and what's worse, they limit the number of search results. So you get around 10 somewhat related results and then they just instantly stop and you get some "you might like these videos as well" results. Frustrates me to no end and I think there could be a great opportunity in somehow indexing videos properly and creating a search engine around it. Then again you'd think Google would've done this but maybe they aren't able to. But in any case I'd prefer an endless stream of semi-related videos compared to their 10 results.