How big of a problem is it? I have reasonable cause to believe one of them let the air out of my tires last night when it was locked in a bike rack. Was on my way home from a long late shift last night after work about 3 a.m. and decided to stop at a 24-hr grocery store and pick up a few things and locked my M-bike up in the bike rack next to an older but high end name brand road bike (pedal only) that was already there and when I came back out fifteen minutes later the other bike was gone and my tires were flat with the valve caps missing. I walked it to the gas station a block away to use their air hose instead of use up one of my CO2 inflater cartridges and the tires aired right back up. Checked the oil and dumped out the gas and filled it with fresh just in-case he had put sugar or something worse in the gas just to be safe (tank only holds about a 1/4 gallon and it was half empty anyway) and checked everything else over really well before taking the 10+ mile trip out of town and all the way home. Seems to be fine so it only looks like he/she just let the air out of the tires this time. Worried about something worse being done next time. I seriously doubt the knuckle head in question has any idea how far I commute on a daily basis and how hard of a ride that is after a very long work night without motorized assistance. Probably just lives in town and his idea of a long ride is only across town (it wasn't a touring bike and it didn't have any panniers on it).