The podcast industry is poised for growth in coming years, according to a recent Mediaweek article. eMarketer is set to release a report later this week projecting that ad spending growth will increase 500 percent between 2006 and 2011.

Analyst James Belcher credits Google for most of this projected growth. The company is expected develop an audio version of AdSense, which would proliferate advertising in podcasts and boost spending.

Despite the small size of the podcast market, Belcher claims that current users "are into it, and they're really into it." Indeed the combination of a passionate user base standing on Google's shoulders seems to be enough for advertisers to begin building their podcast campaigns.

Because of a small user base, advertisers have not been entirely eager to invest in the smaller market, with only 12 percent of Americans having ever used one, according to Mediaweek.

Podtrac CEO Mark McCrery is a bit more optimistic. "They are investing in podcast advertising, getting some good learning and coming back for more." Podtrac has already run podcast campaigns for top companies such as Dell, HBO, and Honda.