I can't believe I was that stupid. That said, I will stop beating myself up in public over this. As Dave pointed out, I even spammed my own blog!
What happened was that Shelfari is a Google creation and when I logged in it grabbed all of my contacts from my Gmail account. That means everyone I have ever sent or received an email from on this account. That includes, by the way, my former boss, her former boss and someone who could have been my boss. As well as lots of people from my synagogue and assorted mail lists. So when I thought I was sending to just a few people who I know who are already on it, I did not see the huge list at the bottom of the screen and neglected to scroll down before I hit send. Call it a slip between brain and finger.
Usually I like the way that all of the Google stuff interacts. One user name, one password. Simple. Not now.
I still haven't even totally figured out what this program is!
Excuse me now while I slink away and go hide under a rock for a few days. This is the kind of thing I lose sleep over!