Xbox live friends offline?

A couple people on my friends list are always offline even if they are online... we send messages back and forth yet for some reason they appear to be offline on my list, but they can see that I'm online. Has anyone else run into this problem?

My friends have checked their privacy settings and everything.

Perhaps they have their status to Appear Offline.FearlessSpirit

yes thats it

they're probably sending their messages through xbox.com

No it is not just about setting to 'appear online', I am meant to appear online and recently none of my friends can see when im online unless i message them or join a party.

:/