[jeffbee]

When I worked in the anti-abuse business, account security was tracked by lurking in organized crime fora and determining the market price for stolen accounts. I don't know what it looks like for FastMail, but I do recall that the range between good and bad platforms was huge. A stolen Google account was like $10, but stolen Yahoo! Mail accounts were more like a nickel per thousand.

[drivebycomment]

You can search for "bulk account purchase" and there are various "sellers" where you can compare the price quickly.