The keys to the rooms at the conference hotel bore ads for the AMC cable channel. And ad fliers were regularly slipped under hotel room doors to promote drawings for iPads, iPad2s and even a trip to a French chateau. The clutter drew the attention of a speaker, Albe Zakes, vice president for media relations at TerraCycle, a company that seeks useful purposes for waste that cannot be recycled. “What is garbage?” Mr. Zakes asked rhetorically. “One answer is, all the cards that have been slipped under your hotel doors this week.”