Friend features in social sites becomes what you want it to be. If you understand how social sites are overwhelmed  by spam, you may start using it with responsability.

If one wants to become "popular" in these sites most people try to add EVERYONE in the world to their friend list. We all must educate people on this: there will always be a spammer that has more "friends" than you. So you must only add those who you really like and know.

For example, in my Twitter account I only add those who I respect, like and have a relationship. These are the factors: if I really know them, or if I truly like what they do. If not, I let them follow but not follow them. If I think they are adding everybody in the world, I report them for spam with no mercy.

The result: I don't have milllions on Facebook or Twitter as friends, but I have the best people there.

It is not a problem of Renderosity if people don't use its features the right way. Also, you should not feel guilty if you don't add someone. He/she will learn, at the medium term, how to behave.
You don't invite to a beer everyone in the street, aren't you?