I heard about it reading tech blog/sites. They already charge cash for an "upgraded" version, though that one breaks along with the regular version. The upgraded version costs $3 per month and there is no limit on the amount of data transferred between + and FB/Twitter, and feeds instantly refresh in the upgraded version (when they're working) instead of having to wait a few minutes with the regular version.
Once they iron out the bugs, I wouldn't be surprised if they kept the $3 per month pay window for added features. They are nice features, but not a necessity as far as I can see.