Yes.
Maybe.
No.
1,The input I've gotten from folks using those rifled bbls and shot is the pattern's history at an amazingly short range. One report was 36" at 5 yards.With the abundance of new and used smoothbore bbls, this is easily solved.
2,It would certainly reduce effectiveness, and possibly endanger non-perps.
3,It won't ruin the rifling, but you'll be scrubbing stuff outa those grooves ad infinitum.