I think you can generally divide "friends" into two groups. The good group helps you out, and they tend to keep in touch even when circumstances prohibit you from seeing them on a regular basis. The other group is only around when they need something from you. The only problem is that it isn't always apparent until you've got more needs than instances to give that you see the difference between the two groups.
I tend to be fairly self-reliant, but how do super-needy people get along through life with friends like that? Maybe those are people in that second group?
On the other hand, he will do just about anything to help those he considers friends, even those who just consider him an acquaintance.
Through an LJ entry I did a couple weeks ago (here's the link if interested: http://www.livejournal.com/users/oldpanther/48382.html), my coasterbud Catherine suggested he might be the kind of person who draws energy from others, and that I, being a high energy person, draws him to me. This is apparently something the book, The Celestine Prophecy, covers. Catherine has lent me the book, and now that cold weather has settled in, I hope to read it soon.
But there are people who are simply takers...and those are the ones discovered when you fall upon hard times. It can be disappointing to discover people you thought were friends aren't really...at least by MY definition. On the other hand, you become more aware of who your true friends really are, and appreciate them all the more.