Some vanity plates will probably attract negative attention. Those that come to mind are the "in your face" type plates like, KISSMYS (kiss my a$$),or IH8U (I hate you), or BETRNU (better than you) or FASTRNU (faster than you), etc. I suppose any vehicle recklessly ripping by, wearing that kind of moniker will be remembered to the detriment of its owner at some point. As a bonus, these plates, while legal, have a tendency to attract the attention of the local constabulary. On the other hand, if someone has a proclivity toward keying a nice car or performing some other senselessness, I am not sure a vanity plate or the lack of one is enough trigger or prevent such behavior.

I have had vanity plates on my cars for years with no ill effects (however I will grant you that I have never had a "fancy" car and I have been a conservative driver...up to now )