I think it will become easier and easier to form relationships (friendships) over social networks. However, it maybe difficult for people to maintain that same relationship. That's until they have tried doing something so many times without being deterred.
I think people will form friendships differently. They may meet a person online. Find out a lot about them through talking to them and reading the information that they put on their profile, and then go to meet them in person. Then, they may let the person know that they know a lot about them (possibly impressing that person) or they may not let the person know that they know a lot about them. The person would basically have to assume that their internet friend knows everything they put on the internet (or that website). Of course, if either person knows things that were not on the other person's profile, such as things said in a discussion with others, then they would be invading one another's privacy. This could be a bad thing. This could let each friend know who the other is.
But, this is something that I think should not be done because you may not feel that you can trust the other person. Both persons may be doing the same thing to the other.
So essentially, the meeting between the two people may be filled with uncertain feelings and more anxiety than a regular meeting of people that let's say meet at a YMCA basketball game to referee.