It's a classic case of "sauce for the goose is sauce for the gander." Marvel made waves earlier this year with a swap offer in which they'd send retailers a rare Deadpool variant of Siege #3 for every 50 stripped covers of DC's "ring books" -- Blackest Night tie-ins retailers had to order in bulk to qualify for promotional plastic power rings for the various Lantern corps -- they received in return.
Then earlier this month, Marvel flipped the script, offering a rare Deadpool variant of the upcoming Wolverine #1 relaunch in exchange for every 50 covers they receive from Marvel event tie-ins, specifically books from the X-Men: Second Coming and Siege events.
An update on our current Marvel book-swap. With one week to go till cut-off, we've gotten less than 15% as many books as we did ring-books. In other words, for every 3 Marvel books returned, we'd previously gotten 20 ring-books. Could be that people wanted the SIEGE variant more.
... or, as one could infer, it could be that the Siege and Second Coming tie-ins eligible for this trade genuinely sold through to readers better than the Blackest Night tie-in "ring books" did, so retailers have fewer unwanted leftovers to unload. But far be it for Tom Brevoort to tweak the competition!