OK well where do I start. I have been on some social networking sites. And I found an old friend and we started talking. And he was being very flirty, and then he ask me out of the blue "What do you think about us being friends with benefits" and I said umm I don't really know. But after I said that he got all weird. And not exactly the same, I don't know what to tell him or even say to him. What do you think I should do.

He either wants to be friends with benefits and he doesn't think you do, it's important to him, he moved on -

OR it was a test to check your moral compass. You failed and so he's moved on.

I assume he knows which it is - ask him.

I wouldn't be fwb because you should come first

He is looking for someone for sex, you were not interested so he has lost some interest.

Ask him how he feels about not being friends with benefits and see how he responds to that