ESPs leaking email addresses

Two of my tagged email addresses started getting identical pharma spam over the weekend. It is annoying me because I am now getting spam in a mailbox that was previously spam free. The spam is overwhelming the real traffic and I am having to make some decisions about what to do with the email addresses and their associated accounts with the companies I gave them to.
One thing I did notice, though, is that both companies use iContact as their ESP. A cursory check of my other mailboxes shows that none of my other tagged addresses are mailed through iContact. I don’t think it’s very likely that these two individual, unrelated companies made deals with the same spammers to sell address lists at the same time. It’s much more likely that there was a compromise somewhere and address lists were stolen.
Edit: Checked my other account and, likewise, I’m getting the same spam to a 3rd address serviced by iContact. I’ve sent mail to all 3 companies involved and we’ll see how they react.
And, as I was thinking about this, iContact just laid off a bunch of staff about the same time they announced their partnership with Goodmail. Based on past history with companies in this situation, it seems possible this is a disgruntled former employee. I’ve also seen reports from other people noticing spam to addresses given to iContact customers.