In the specific case of spam, some data...
In the last month, we have the following number of posts reported as SPAM by our membership (broken up by sub-forum, highest to lowest):
General Discussions: 20
News: 9
Amazon Kindle: 7
Lounge: 6
Reading Recommendations: 6
Deals, Freebies & Resources: 4
Sony Reader: 4
Apple Devices: 3
Introduce Yourself: 3
LRF: 2
Which One Should I Buy?: 2
Alternate Devices: 1
Autres liseuses: 1
Barnes & Noble Nook: 1
Bookeen: 1
Kobo Reader: 1
More E-Book Readers: 1
Reading & Management: 1
Visitor Messages: 1
TOTAL: 74
This does not include the few (about 1 a day) auto-captured by the auto-moderation part of the software, nor stuff we manage to find ourselves and delete before it's reported (which is a sort-of game too

). It's probably a reasonable representation of the spread though.
I'm of the opinion that SPAM is not that big a problem here. It's reported, caught, or just discovered by mods, and spam-ban-and-deleted pretty quick. It's certainly one of the easier, (enjoyable

) auto-pilot parts of Moderation, because there's simple process set up along the lines of (1. Delete post as spam? Y/N, 2. Delete all posts and threads started by user? Y/N, 3. Ban user? Y/N). I think it might be a distraction to the "trolling" and "sockpuppetry" issue...not an unimportant issue, of course, but one that is less a part of this issue, no?
Cheers,
Marc