It wasn't clear to me if you're just mentioning in your posts that you would like to be friends or if you're inviting people directly through their profiles. I also wasn't totally clear as to what you consider an "online friend." Someone to chat with here on the site, someone to IM and email with, or something more substantial?

Bear my confusion in mind as this response may wander a ticky off topic as a result.

First, good for you for posting and getting into discussions here on the forums - great first step. If you're only offhandedly mentioning your desire to be friends in these posts, however, you might just be approaching this a little too passively. Sometimes, people need to be slapped upside the head with what you want from them before they will accommodate. Post an add in the personals section stating clearly what you're looking for - that section can be for friends as well as romantic relationships. Of course...lol...this post may be just as good to get the point across...

If you are sending friend requests through other user's profiles, start by striking up a conversation in the person's comment section first. I must turn down three friend requests a week because I have never spoken to the person one on one, even if I have seen them around. On the other hand, if they leave me a comment as to why they're dropping by my profile, I'll respond and we can chat a bit. I'm one of those funny people that just happen to like to know a persona little bit before friending them.

One other suggestion is to respond to new users' introduction posts. Say "hi" and offer to add them as a friend if they're interested - that's a great way to get together with other folks just finding their feet in the community.

Good luck!