..Sending announcements to -users doesn't seem more appropriate to me than spamming grabbed email addresses...
Same as others, I have no problem with Cocoon-related commercial announcements on our lists provided
a) sender is in some way a member of the community
b) such messages are clearly marked for example with [ANN] (or maybe a new [BIZ]) marker in the subject
c) the number of such messages stays low.
-Bertrand