Microsoft has come up with a good example of how you should handle the process of deprecating data.

Have a look at my MVP profile here.

You'll see that in a lot of profile entries for speaking engagements, the string "RETIRED -- DO NOT SELECT" is shown. Why is that? Very simple: at some point the selection ".NET", for instance, was a valid one, but now it had to be changed. Of course there are approaches to retiring data that would have left the old strings in place, but then those mechanisms introduce considerable overhead in the data gathering process. As the strings that are shown now also include the old strings, there was no conceivable reason not to go the easy way.

Thanks to the unknown delevoper/db admin who published this great sample!