The FCC is investigating Apple's rejection of Google Voice iPhone app and other apps to its app store.  The FCC has sent letters to Apple,  AT&T, and Google to investigate the matter. They have been getting a lot of pressure from consumer and activist groups to look into the practices of carriers and exclusive deals.

Google Voice is a suite of phone resource products that acts as a switchboard, voicemail and router service.

The letter to AT&T asks:

Are there any terms in AT&T's customer agreements that limit customer usage of certain third-party applications? If so, please indicate how consumers are informed of such limitations and whether such limitations are posted on the iTunes website as well. In general, what is AT&T's role in certifying applications on devices that run over AT&T's 3G network? What, if any, applications require AT&T's approval to be added to a device? Are there any differences between AT&T's treatment of the iPhone and other devices used on its 3G network?

"Recent news reports raise questions about practices in the mobile marketplace," FCC Chief Julius Grenachowski stated. "The Wireless Bureau's inquiry letters to these companies about their practices reflect the Commission's proactive approach to getting the facts and data necessary to make the best policy decisions on behalf of the American people."