Wired points out that product placement in TV shows went up by 84% last year - the impact of TiVo and similar devices (I expect most of the upsurge was from cable provide boxes). It seems that the writers and actors are confused about where the money comes from:

TV networks are turning to product placements to fight back against ad-skipping technologies like TiVo, but now some writers are putting up a fight, demanding more pay in exchange for scripting product plugs into their shows.

The issue sparked open protest last month, with both the Writer's Guild of America and the Screen Actors Guild calling for a "code of conduct" to govern the use of stealth advertising.

Code of Conduct? I fail to see how a product placement is more offensive than "message" storylines. Not to mention that the writers are forgetting where the money comes from. Until the iPod model takes over, it's still coming from advertisers. Like newspapers, they aren't reacting that well to disintermediation.