Patent was submitted in 94 and I think granted in 97. It may be a consideration.Someone mentioned in this forum that since MTG was released more than two decades ago, it holds no copyrights to its "concept" commercially. They can sue them for using identical logo or name, but not gameplay. I think.
Think this is the original submission :
http://patft.uspto.gov/netacgi/nph-P...&RS=PN/5662332
Someone translated that into layman here :http://howell.seattle.wa.us/games/mtg/patent.html
As far as trademarks are concerned I think that covers the 'tap' symbol and most graphics.
I've come to believe they've reached an agreement with WotC to pay them for some sort of license, which a lot of CCGs have done but not made public.
Also wouldn't surprise me if WotC or someone else tries to buy out Cryptozoic.