The difference is that The Hobbit plot is widely known, the book it's based on is a classic. With Skyfall, they are keeping their cards very close to their chests - so when it's finally released it will be that much more special, exciting and surprising.
I like the way we've been drop fed news, with the clapperboards (a really good idea which got fans talking without giving too much away), production blogs that showed a lot but revealed very little. The images revealed have been very ambiguous, again getting fans talking and theorising. The same with the teaser.
I feel that EON, or whoever is in charge of promotion, are doing a very good job and Bond fans who are used to getting a lot more information are just getting a little impatient.
Agreed - we're not actually "entitled" to anything and it has built up an air of mystery (cretins posting script excerpts here notwithstanding).
Good point about The Hoobit - as much as anything that publicity seems to be "look how [x bit from book] turns out". Different idea.
I suspect if they were remaking, say, On Her Majesty's Secret Service, more would have been shoved out there; but it is nice that it's all quite mysterious really.