Search aggregation. Where do I begin. Ah yes, Webfeat. I'll slam Webfeat.
My opinion on this sort of thing is: if you know what you are looking for, look for it in the proper place. Searching unrelated, specfic sources of information for a single topic is a waste of time and resources. I believe effort would be better spent in educating people and presenting the information in such a way that they are able to identify what information exists within a particular resource, instead of blanket searching across all of them.
As far as Rollyo goes, if you know what site you are interested in, you don't need a Rollyo account. can add the words "site:whatever.com" into the query box on Google and only search the contents of site.
This is beginning to look a lot like the old pre-crash web bubble, except none of these sites are actually spending money on anything except bandwidth.