Tweenbots are human-dependent robots that navigate the city with the help of pedestrians they encounter.
Here’s an interesting article about online ads.
http://adblockplus.org/blog/anatomy-of-ads
My takeaway from the article is that unless you run an ad blocker, your online habits tracked and you will wait longer than necessary for pages to load.
There was no spam in the month or so after I installed 2.7. I assume that 2.7 broke spam scripts (different URLs and form parameters maybe?)
Anyway, spam is back again, not sure why. So far Akismet caught everything, never had a false positive.