Friendship's value

[it]

Over periods of time of socializing I tend to accumulate friends, people I have fun with and bond with and will be helpful towards. Then something will happen - a situation where I am the one who needs others - and it will act for me as a great filter, a relationship extinction event that only the strongest friendships survive. I know it's not a realistic sentiment, but somehow in my mind not all allies in life have to be my friends, but all friends have to be allies. A friend who doesn't give a shit is... Well, not much of a friend.

What do you do with "friendships" that turn out to not be as genuine as you would have thought? People who like to hang out with you, perhaps find you enjoyable or entertaining or like your insight, but will not actually be there for you when you need them or act with your best interest at heart, even after you have being there for them?

Do you break it off? Do you stick around but keep them at arms length? Do you resent the "bad investment"? Do you feel like it's ok and you've just learned your place and where you stand with them and can now keep that in mind? Do you stick around for the sunken cost? Do you go out of your way to get rid of them?