Logbook audits are not real common unless you've had an accident and the insurance company is doing its best to deny coverage. At which point they'll try to match up 8710s, aircraft maintenance logs, credit card receipts, cancelled checks, whatever they can find. For any rental aircraft, there's usually a paper trail to follow. For privately owned aircraft, it's much more difficult, but if you say you flew 500 hrs in a plane during a period that the plane had only one 100 hr inspection, well, that's a tad suspicious.