Lots of flats commuting on the streets of Los Angeles (and Norwalk); just had another yesterday (small sharp bit of glass, that one). I use Schwalbe Marathons on my DaHon folder commute bike (16" x 1.75) and have had flats from small sharp metal wires, a nasty sheet metal screw and glass; apporox. one flat per 10 round trip commutes. Plus I had one Schwalbe tube fail at the valve.
On my road bikes, fixed gear bike, mountain bike . . . far better luck. One goat-head on the GURU on the way to climb Palomar, glass from the MUP on the fixed gear, a thorn on the rear of the muntain bike (but that may have been before April).
Rick / OCRR