Vsplash,
With the older 2.x release, at one point, we had great validation. There will always be a few with JFBConnect as the Facebook namespace doesn't validate properly by default, and that's something that Facebook would have to correct. We added a task to update our links to use & instead of just & in links. However, the validation errors we introduce do not cause any issues in any broswers that we're aware of, and Matt Cutts from Google has specifically said that Google doesn't care about validation for search engine results (Even google.com doesn't validate):
Hope this helps clear up our stance. If we get more subscribers that demand 100% validation, we'll focus on it more, but efforts like this do take away from feature implementations, and I think most users would rather choose the latter.
Thanks,
Alex