In the beginning (or near it) the FCC restricted cell phone operators to 2 carriers in most markets to ensure competition but also foster growth. It wasn't long before their own studies indicated that no real competition existed in a given market until at least 3 carriers were present.
This deal has the potential to effectively put Sprint out of business, leaving only Verizon and AT&T.
I hope the FCC won't forget that lesson they learned.
Just look at current pricing for iPhone or iPad service from AT&T and Verizon. The minor differences in their offerings amount to variations on a theme, not competition.
If the iPhone were to also come to Sprint and/or T-Mobile, I would expect to see more competitive pressure on all carriers in their service offerings.
Also, the FCC originally required all 1G cell phones to work on every carrier's network—to ensure portability of service between carriers. That is a requirement they were talked into dropping when 2G was rolled out, creating the current situation of AT&T's phones not working on Verizon's network (and vice versa). There is hope that '4G' LTE might end up fixing the portability problem created when the FCC dropped that requirement. Even Sprint is now mulling a '4G' LTE option in addition to its current '4G' WiMax offerings.
Personally, I'd rather the merger not get approved. I see it as a short-term fix to AT&T's current perceived problems, with significant long-term negative consequences in tow (i.e. the marginalization/elimination of Sprint).