Big Brother is watching

Three years ago or so, we were told to hang tags from our cars' rearview mirrors to prove that we're entitled to park where I live. When I picked up my tags, I specifically asked who's responsible for monitoring their use. I was told we (the residents) were. So, essentially, no one. Sometimes I remembered to hang mine, sometimes I didn't. Until today, when I received a notice of non-compliance in the mail from the homeowners' association and the threat of fines if I don't remedy the violation. Seriously? My neighbors know my car. Clearly, so does the association. How else would they know who wasn't complying?