I guess the closest analogy here is to CPM (cost per mille - thousand page views), for online display advertising. On that scale, $0.80 CPM is low; typical figures I've seen/heard are around the $10 mark.

That's probably related to the fact that Twitter is still relatively ad-free; it also means they have a lot of ceiling into which they can increase their revenue, albeit at the usual cost of negative user experience!

Has anyone here worked in advertising for social networks which use timeline-style feeds? I'd be interested to hear how (and if) the businesses practices differ from 'traditional' online advertising.