I e-mailed everyone on my customers' mailing list to let them know about the competition here on the blog. I sent them out in batches of 15 or so to make sure it didn't get stopped at the server as "spam". I accidentally put the e-mail addresses in the CC field instead of the BC field.
I apologise unreservedly for such a stupid blunder, I'd certainly understand if anyone got cross about other people that they didn't know seeing their e-mail address but my customers are such a lovely lot of people, I haven't received one complaint. I assure you that it won't happen again.