I've had an influx of NPB's lately, too. One item, is currently listed for the THIRD TIME! Two NPB's on it. ARGH! I'm more than patient - but I have no qualms about filing, and leaving negative feedback if necessary. They can retaliate - a neg doesn't hurt me so much since I'm over 1000.
I used to not allow zeros to bid - but my husband talked me out of it. Remarkably, my NPB's mostly aren't zeros!