I believe the aging of beer can be effective with specific styles like Barleywine, RIS, Sour Beers, etc...
I prefer to drink my IPA's , APA's and lower gravity ales young but that's me.
Alot of things come into play with this issue. It depends on the style of beer as well as one's own tastes.
There are also other factors that can come into play when aging beer, the handling and processing (i.e. oxidation) of beer can adversely affect the long term storage as Keith has indicated.
The long term storage of beer will slowly oxidize at varying rates depending on the storage technique and temp. Your strong beers (like barleywines, tripels, dark ales) will be their happiest at room temperature (55-60F), most of your standard ales (like bitters, IPAs, dobbelbocks, lambics, stouts, etc) will be at cellar temperature (50-55F) and your lighter beers (like lagers, pilsners, wheat beers, milds, etc) will be at a refrigerated temperature (45-50F). Usually the higher alcohol, the higher temperature and lower alcohol, the lower temperature.
Again, it depends on the beer style and your personal tastes as to the method and duration of storing beer for the long haul.