In my opinion, besides the psycho ex's, the quickest way to get keyed is by being inconsiderate (not saying you were though!). Here in Los Angeles where parking is often competitive, people squeeze their pimped-out Hummers into "compact" parking spots or simply occupy two spots. Parking properly and not pissing people off where they can follow you to where you park can be great deterrents. Then sadly there are those who see something pretty and feel the power in deflowering it. I call these people "clients" (I'm a therapist).