Author of the original article here. I guess I should have said that I never glance at the Gmail ads and I have a hard time imagining why anyone would, as they are consistently irrelevant to me. As soon as I learned about a plugin that could replace the ads with something useful, I installed it.

On the other point that seems to be getting commenters riled up -- "messing with other people's content" -- I think I am on Rapportive's side. I admit that I would be seriously annoyed if someone wrote a plugin that replaced my stories on Xconomy with, say, TechCrunch stories. But that's the risk of publishing on the Web, where the viewing platform is not ultimately under your control. And if people started using such plugin widely, it would be useful feedback for me -- it would mean that I should do something to make my own stories more interesting. Google should see Rapportive as a signal that something is missing in Gmail. Either they should provide more relevant ads, or they should copy (or buy) Rapportive.