Is there such a thing as too much publicity?

OK, we all know part of the reason advertisers spend $2.5 million on a Super Bowl ad is so they can leverage the extensive pre- and postgame publicity. (And if they don’t, they’re not the sharpest knife in the drawer.) But now I’m beginning to wonder how much pre-game publicity is too much.  Particularly with the advent of streaming video, it’s increasingly easy for everyone, not just people who cover advertising, to see substantial parts of many of the spots before the game. Does that make the airing of the ad in the actual game anti-climactic? Is it possible to give too much away before the game?