
Amanda Spinks told us at a talk that search engines usually have a 5% overlap in terms of hits. What this means is that searching is an art more than anything else -- what we come up with really depends on the tools, techniques, experience, and expertise of the searcher. (And dare I say, a certain element of luck, too).
Take a look at GahooYoogle, a nifty search engine which allows us to see results of both search engines, side-by-side. Does this make searching easier? Not really. In my opinion, if you want to do that, then go for a meta-search engine. But if you want to see how the magic of the Google algorithm works compared to another "normal" search engine which uses keyword searching, then try this out.
Do you notice something? One can simply type in the article's full title (or even parts of it, provided it's wrapped around with "quotations"), and wham! there you go, the first few hits will usually lead you to the full or abstract, whereas in a search engine such as Yahoo!, you'll have to work a lot harder to find what you're looking for.
Ah yes, what can't Google do? Another reason why it's still the information professional's best friend.