Really simple to decode the image. What I'd worry about is rate limits and whatnot.
Well look at it this way...
EVEN if it goes for 1 email a minute...
You scrape the emails from a LARGE group, and set it for a day/night
24 hours = 1,440 Emails
+ If you run 2, 3 or 4 programs at once... You can easily collect 5000+ emails every 24 hours.
Then since you have the emails, you can send 5000+ invites right away and Facebook won't care since its through there email and Facebook thinks that IF you have there email, its fine to add as many as you want