Personally I think it's broken just because reviewers let their personal bias affect their reviews. I can't see Swag bags having much affect when they have to stay at the office. Still, there are a lot of games who's reviews are ridiculously off-base, and you have to wonder if they were paid off.
A good example for that is Final Fantasy XII. It's one of the worst Final Fantasy games ever made and honestly just a horrible RPG in every way. It's plot was bad, it's music was unmemorable, it's characters were horrible, and it's gameplay could be set to autopilot.
Then there are Gamespot's reviews. To summarize their Metroid Prime 3 review: It does nothing but improve on the formula of the last two games but since it didn't change much we are only going to give it an 8.5. Then they reviewed Halo 3 and said: It does nothing but improve on the forumula of the last two games and it didn't change much, but that makes it great! 9.5! Not that Halo 3 doesn't deserve a 9.5, but what's the purpose of a review system with no consistency?
It's not just gamespot either. Most major review sources are the same way. Another good example is The Godfather: Blackhand. Yes, it's a GTA clone, but if all that mattered in reviews were the quality of the game itself then it surpasses GTA in every way. The game is longer, the combat has so much more depth it's not even funny, the AI is better, the plot is a lot better, and there is more replay value. The only thing that's worse about it in comparison to GTA is that there is a much less diverse selection of cars and weapons. Not that the weapons matter when the combat system is so much better. Either way it hardly deserves 2 points lower from reviewers.
I agree that the system is broken. I don't think review guides, temporary score embargos, and office located swag bags are the reason it's broken. It's simply an industry that caters to the hardcore and ignores anything that's not big-name and doesn't have millions of dollars behind it. Think about what's going to happen at the GOTY awards for each site this year. You think Bioshock, Mass Effect, Super Mario Galaxy, Ratchet and Clank, or Super Smash Bros. Brawl have a chance of winning? Of course they don't. Every single site is going to give GOTY to Halo 3 regardless of the quality of any other game because giving Halo 3 GOTY is what will increase their site traffic.
It's not something that you can fix though. About all you can do is stop using review sites that give off these bad reviews. It's worked for 1UP, who's site traffic and magazine subscriptions have gone down so much due to their perceived hatred of Nintendo that they are about to go bankrupt. Gamespot has similarly entered some recent financial trouble. The solution is simple: Trust your own experiences with games rather than stupid reviews. Or, maybe trust the experiences of a friend who you know. Read the content of some reviews you do trust, but don't go on just the score. See if the problems with the game are problems that affect you. See if the good things about the game are things you care about. Play what you enjoy, and ignore the idiotic big name sites that cater to big games.