I'll be honest, sometimes I fail review audits.
But will failing a certain number result in something happening? Will lose my review privileges or reprimanded? Will I be cast into the gorge of eternal peril?!
If you only fail once in a while, that's not a problem. Some of the audits are really hard to identify as such (or correctly pass, for that matter), because they're based off individual decisions, not necessarily agreed-upon policy.
If you fail too many – and nobody really knows that number – you will be temporarily banned from reviewing only. No other restrictions will be in place, so it's not comparable to a full account suspension.
The algorithm is as follows: Given a 30 day window, the first ban will get you 2 days. The second one 7 days, and the third one 30 days.
Note that automatic bans are only in place on the trilogy sites (Stack Overflow, Server Fault, Super User). Moderators can still always manually ban users if the system didn't catch them.
Let's start with the obvious - you will be banned from review audits if you get too many - here's the official SE staffer post on the subject - it says the ban is up to a week, and the comments to this question state this is a temporary ban of up to 30 days.
On the other hand, review audits aren't designed to punish people with good intentions - they're designed to solve what many folk (myself included), consider a problem that's more prevalent on some of the other sites - people robo-reviewing for badges.
If it's occasional, chances are you won't get the proverbial rap to the knuckles. This is designed to prevent industrial scale misclicking.