I'd be more than happy to see this, with the added caveat that anyone that returned address space to ARIN that was subsequently marked as 'contaminated', should undergo a review process when attempting to obtain new address space. Charge them for the review process
Anyone that intentionally uses address space in a manner that they know will cause it to become contaminated should be denied on any further address space requests.
Another option, is to hit them where it matters. Assign fines and fees for churning address space and returning it as contaminated. Set the fee's on a sliding scale based on the amount of contamination and churn. the more contamination, the higher the fee.
It would be problematic in some dimensions, but it seems that perhaps allowing them to return space in exchange for a larger block is part of the problem, and maybe part of the answer would be to make them retain the block and only allocate an additional block. Route table growth and all that, of course. An alternative could be to delegate them a larger "contaminated" block and allow them to incur the expense of cleaning it up(*). * And I say that kind of tongue-in-cheek, since I don't really believe it to be easy to clean up a block once it is contaminated, due to the sheer number of local blocks, etc., which may exist. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.