I rarely use them and usually give my Hotmail addy out to places so if I even get notice of a PM , it could be days before I look at that secondary addy. I don't really see the difference between that and being able to e-mail except:
1)On a widely viewed forum you have a layer of protection. People can write to you but you don't need give out your address.
2) Gives you the ability to personally talk to someone whose e-mail address you may not have.
We are a fairly tight group here, but that could be a strength and a weakness. We know or could easily get someone's e-mail if we really wanted it. it does tend to make us a closed group of friends rather than a growing, viable forum.
I would have PMed Suz to see if she was OK since we haven't seen her here in a while.
I often get pissed when someone "kindly takes it off forum" to explain something personally to someone else in a thread I was following. PM-ing can be clique-y that way. Some forums are stringent about keeping on topic. (Fascists!)