You're so right about this, when you tell your family or friends to buy bitcoins as an investment they look at you like there's something in it for you, which is not the case, so what I do now is try to educate to them what bitcoin is as a currency and how it will change the way we keep/spend the money in future, if they see something in it, they ask me themselves how they can buy it and then I point them into the right direction, if not, then I don't mention it to them ever again. So don't persuade anybody to buy it but do educate anyone you can.
To add another point - in general people will tend to blame you if their investment does poorly, and in Bitcoins case it has a tendency for rapid high/low movement in the space of a few days. You don't really want to turn a friendship into something sour because people think you're trying to sell them something that turns out to hurt them.
IMO, if people are interested by all means talk and tell them about it - but if they don't care/interest doesn't lie there I wouldn't spend to much time on it. They'll come around if Bitcoin does make it big and if it doesn't nothing lost.