I think it would be quite useful on 24x7 systems. Anything else, you probably have downtime that could be used to rebuild an index if you find it really was useful after all. But for large tables that are being constantly accessed, the ability to make one unqueryable while still maintaining data in it, and monitor the performance impact of that over a period of time, does sound useful. If you've suggested this on MS Connect, please post the link and we can all vote for/against there.