"Legislative gridlock" is a weak excuse. Plenty of legislation gets through, from PPACA (which had, and continues to have, widespread objection) to USA FREEDOM (even if you claim PATRIOT's expiration was the result of "deadlock", the replacement came a day later) to JOBS (specifically legalizing things that startups wanted to do!) to allowing people to unlock their cell phones (not really a Big Foo priority). If the people really want Uber and Airbnb -- which they seem to -- why can't they just get a law passed? And why can't all these innovative, well-funded startups figure out how to disrupt and fix something as obviously dysfunctional as our political system?
My worry is not so much with these particular ways they're breaking the law; it seems like this is probably reasonable (though I'd still like someone other than Uber to consider it). My worry is with the loss of the rule of law, and the precedent that we're not going to care about whether the law is followed. It's certainly true that Uber et al. aren't the first companies to break laws, but this seems like a qualitative change in what laws are being broken and what the impact on society is, and a democratic society should be able to have an opinion on it.