twtAd made it into the Dutch media.
TwtAd: Geld verdienen met je tweets Marketingfacts
twtAd: Geld verdienen met je tweets | Site van Pieter Bas Elskamp
The author gives a review and reports no loss of followers but is not so impressed by the revenue. However, his tweets have less than 1000 followers.
I guess similar concerns were raised years ago when people started to advertise on their own websites.