From what I remember, if you have panic attacks only in social situations then it's social anxiety disorder. I think there are a lot of people on SAS who don't actually have the panic attacks, so maybe theirs is milder. (I've had them for years myself, but now I am so good at avoiding the situations that bring them on, I don't have them anymore)
And Panic Disorder is when you have panic attacks that are not apparently connected to any certain situation. These people have them anywhere, anytime. Eventually they can be embarrassed to the point of not leaving the house because they never know when or where another attack will happen. But with social anxiety, we KNOW what specific situations to avoid so we don't have an attack.
I got my degree in Psychology in 1999, but haven't read the DSM-IV lately. Maybe it's changed, but I don't think so.
I have panic disorder more so than social anxiety and with me it doesnt matter the social situation, around people, or alone....I can get attacks whenever. I had a horrible attack yesterday morning....probably my worst in a year+....and that was just waking up and getting out of bed.