Facebook shows you a list of your best friends, people with whom you interact the most. Hi5 shows you an alphabetical order and gives you the task of finding what’s relevant to you.
What do you think Google shows you when you Google “fejk sdfjk vsdn dfkj“. Does it show you “we don’t have any relevant results”? No, it says: “Showing results for fjk fjk vsdn dfkj” (this is an altered version of my query), instead of saying: “No results found for fejk sdfjk vsdn dfkj”.
So, instead of saying “we found nothing, how about you refine your search”, Google refines the search for you, takes a chance by changing what you have typed, and gives you the right result.
You may say “but this is minor, it’s a small thing what Facebook / Google do”. At this single level, perhaps. But you think of all the thing Google tries to get right from the first time, without waiting for human intervention, if you think how much effort Facebook puts on trying to give you exactly what you expect of it right the first time, then the changes are not, by all means, minor.
I dare saying that Facebook is much more successful than Hi5 (and others) and Google is much better (the user usage prove it) than Bing (and others) due to small things like these, on a higher level.
Note: Also see the Yahoo! Group on which I present similar issues: IMRo. To join, email email@example.com and reply to the confirmation email.