I am pretty against mandatory posting.
Tournaments are reused and recycled. By having decks posted, people can look back and see the meta/winning decks and just use those. Its cheap and scummy but ya its gonna happen.
Whats the point of posting decks? Legality check? You should be able to tell a decks legality when you play it.
Also, for people like shockcannon, Oa, and myself, we speedbuild a lot of tournaments. i dont save those. Im speedbuilding a deck every 15 min i dont have time to sit and organize what decks i used and who i used them against.
I am firmly on the stance of optional deck posting.