It would only be wise to remove a placement if your business model is to NOT make money.
If you run a fully transparent network, there will be an advertiser for all placements.
Just today I read an old thread on BHW about how adbombo (or whatever it's called) hotlinked videos from xvideos. Xvideos put a stop to that but still allowed them to embed even though they lost money by doing so, but they were willing to do so for the exposure.
Yea, if it is just you buying ads and you look for conversions, you should just have unlinked the placement and let him run his passback for as long as he wanted - probably losing 5-10% in impression loss
Problem solved before it even made it to GFY!