The Maryland General Assembly had a good ides. They said "Let's screw everybody who isn't paying attention and willing to jump through hoops". Of course, they didn't phrase it that way, but that is the net result of their action.
You see, most homeowners in Maryland are eligible for a "homestead tax credit" which limits the amount your property tax assessment can increase in a year if you actually live there. They think that people who don't live in their homes (i.e. rent them out) are getting the tax credit and shouldn't be. They further say (on their FAQ) that "The only way to verify residency of the homeowner is to require an application and have the filer provide his or her Social Security number." Too bad all that really verifies is you took the time to fill out the form, not that you live there. They could just check your MVA and state tax records and automatically give it to you if both match the property address, but no, that would make sense.
Most people get their property taxes taken out of their mortgage escrow account, they never directly pay the bill so, many people never look at their property tax assesment. If you don't look at it, you don't see the form, you get hit with the full increase.
Worse yet, you can't just fill out the form now and get it out of the way. You have to wait until they mail you the form, sometime between 2008 and 2010. Good luck remembering that for the next couple of years. They do actually have an online version of the form, (using internet explorer is recommended) but you need the 8-digit security access number that comes on the printed form.
More information at COMMONLY ASKED QUESTIONS ON THE MARYLAND HOMESTEAD TAX CREDIT APPLICATION