SAN FRANCISCO, Jan. 5 — It bears the hallmarks of a classic urban scourge: back-channel sales, assaults on enforcement officials and even death.

It is the price of parking in San Francisco.

Burdened with one of the densest downtowns in the country and a Californian love for moving vehicles, San Franciscans have been shocked in recent months by crimes related to finding places to park, including an attack in September in which a young man was killed trying to defend a spot he had found.

More recently, the victims have been parking control officers — do not call them meter maids — who suffered four attacks in late November, and two officers went to a hospital.

Over all, 2006 was a dangerous year for those hardy souls handing out tickets here, with 28 attacks, up from 17 in 2005.