When I joined WELL they had introduced forums that were only intended for people who joined during a specific calendar year. Presumably it was an attempt to try and counteract the effect somewhat. Personally, it just made me feel ghettoized.
At an old-fashioned web forum I used to run we toyed with the idea of closing down and archiving old threads after they reached a certain age. The idea was to try and codify our opinion that old conversations might be worth preserving for posterity, but they aren't a substitute for new conversations and shouldn't be used as an excuse to stifle them. Never actually got around to implementing it, though.
At an old-fashioned web forum I used to run we toyed with the idea of closing down and archiving old threads after they reached a certain age. The idea was to try and codify our opinion that old conversations might be worth preserving for posterity, but they aren't a substitute for new conversations and shouldn't be used as an excuse to stifle them. Never actually got around to implementing it, though.