(wandering over from, hilariously enough, a pingback)

Nope, separate features. Pingback is an automatic comment from pingback_bot saying, essentially, "Hi! iamashamed just linked to your public entry! Thought you'd like to know!" (assuming we both have pingbacks turned on, and both entries were public at the time the ping was sent).

The Facebook/Twitter thing is "Hi! You know me and love me on Facebook/Twitter; I'm sure you'd love to know that I just made an entry/comment on LiveJournal, because all of my Facebook/Twitter friends know where my LJ is and care about the stuff I write entries about, and also would like to follow me around and reply to my comments in the journals of complete strangers!"