
Its sad, but building decay is becoming a major issue for some U.S. cities on the East Coast and Midwest. Many architecturally significant buildings stand vacant in economically depressed or otherwise undesirable areas and as they approach 100 and 150 years, the elements begin to slowly take their toll.
Alan Weisman's book The World Without Us goes into great detail on how long human structures can last when we aren't taking care of them--and once water is allowed to enter a structure, it usually isn't very long.
Baltimore is fast becoming a perfect example of what a city with too many forgotten buildings comes to look like. The suspicious empty grass lots to be found at the corners of blocks in certain Baltimore neighborhoods are not the planned gardens and green spaces they might appear to be, but actually uncontrolled, "natural", like-it-or-not demolition of the city's built heritage.
A good example of this phenomenon can be seen on Google streetview here.
Is that what the corner of Greenmount and Preston will look like in 5 years?
Here's the corner of the block (courtesy Google) before this week:
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..and as it is now.

It may not have been a building worth preserving, but I doubt it was a building worth demolishing. I think that during a period in which people put so little thought into building sustainably (see: suburbia) the loss of even one medium density building with potential charm and a real history is sad. The funny thing is, these buildings were the suburban tract homes of the 1910's!--except then they were served by streetcars and supported a denser population.
A cool site I discovered recently, Built St Louis, discusses this issue in depth as it occurs in St. Louis, MO. Both Baltimore and St. Louis have been struck by similar historical misfortunes (B.S.L. outlines them very well here.) including white flight to the suburbs and the resulting population loss. In the 1950's Baltimore had a population nearing a million. That number teeters around only 650,000 today. Nobody's left around to take care of all the elderly buildings. sad!
-G