Hi Justin,
One problem has only just now crossed my mind. Traffic constraints.
I like being able to block as many connections as possible when I'm connected via cell phone, via which the traffic is expensive. This includes turning off images, styles, et al. If pages started establishing additional data connections behind my back, I wouldn't be happy.
Perhaps info bar isn't required for WebRTC-aware users. But as it'll be a new feature to many users, some of them may grow angry that a subset of pages is permitted to generate unnecessary data traffic even if they blocked images, stylesheets, video, audio and plugins.
And it'll grow harder to inspect what traffic web pages are generating.
Whether or not this subset of users is significant enough to warrant worrying about them, that's another thing. But I don't think bringing this to your attention can be a bad idea.