"Never loan money to a friend with the expectation that you'll get it back, be ready to just let it go."
To hnriot, who I can't respond to: No, it's not being a chump to willingly give money to those you are close to. The other side of the "be willing to give money to friends" coin is "be aware and careful of who you consider friends". You may be a chump if you give money to people actively taking advantage of your willingness to do so, but those people aren't friends. You should never give money to people who aren't your friends, and you probably shouldn't loan it to them either, unless you're in the lending business.
Also, I agree with everything you said. ^_^
One of the two founders of Genentech was a good friend of his, and so he had the opportunity to put the first money into what became Genentech. But he refused to do it because they were good friends, and instead helped him find other investors.
Somehow I don't necessarily see something like this happening often in today's funding environment.