Launching a site quickly around an idea to claim a first mover advantage is rapidly becoming a mantra for new Web 2.0 startup sites.  As new social networks and other types social media tools on websites pop up – many are simply exploring an idea quickly to see if it sticks, and aiming to put in more work to redesign or add features at a later stage.  Added to this is the large number of sites that have grown their audiences before the rise of Web2.0 competitors (and the increasingly formulaic design of Web 2.0 sites).  The result?  Redesigns are inevitable.  Technorati and Yahoo are just two of the many sites that have gone through recent redesigns to update an interface.  The only problem is, no matter how bad an interface is – once someone starts using it in that form, they are used to it.  The classic example is the keyboard, which was originally designed to slow down typists by placing common keys as far apart as possible.  Of course, people adapted, and every attempt now to replace the QWERTY keyboard has failed, despite the fact that new designs may be superior in every way.  Sometimes what people are used to wins despite every logical reason to switch.

If you put the rising number of sites going through redesigns together with the fact that older users will always have adapted to your old interface – you have the New Coke vs. Coke Classic conundrum.  For most of these sites, the new version sticks around (unlike Coke), however the necessity of keeping your "classic" version will be increasingly common as sites allow their longstanding users to continue using an older version of an interface that they are more comfortable with.  Yahoo has done this very well with their upgrades to Yahoo Mail – I am still running the "classic" version for my personal account.  Technorati has tried to take some steps towards this with, but hasn’t quite succeeded as some features users used to use often seem missing now (even if they are not).  In either case, the real question seems to be how long is reasonable to keep a "classic" version of an interface around.  I’m not talking about the screenshots you can get on the Wayback Machine – but a fully functioning old version of a site.  You certainly don’t want to move ahead into the future updating two versions, and at some point the older version will be out of date.  Is it better, therefore, to just force all users to upgrade and use the new version?  Or should sites follow the old adage of giving their users what they want and avoid the possible fate of New Coke and their new interface being rejected?  As a user or a site creator, what do you think?