Two "makes you go 'hmm' factoids from CTIA cell usage report

Pouring over the CTIA's U.S. Wireless Industry numbers for 2006, (grab of page 4 of 10 at top) I've noticed a couple of trend lines that are more than a little curious.

I'll mention these now, and then ask for your opinion.

First, you would think that with the year-by-year growth in cell subscribers and minutes, we'd have more cell phone towers year by year.

Interesting that we lost nealry 2,000 cell sites between June and December, 2006. Hmm, maybe there's modernization going on, and older towers have been decommissioned in favor of newer ones with greater coverage areas?

Second- the long-term trend continues of roaming calls being longer in duration than local calls. The difference is noticeable- around 45 seconds or so.

Two possible reasons:

Roaming calls may take longer because the crisp quality of local-to-local calls is not available, driving callers to repeat what they have just said, and/or

The very fact that a call is being placed from out of town drives the conversationalist to describe where they are and that they are OK ("the flight was a bit bumpy but here we are, and the restaurants in this town are great")- descriptors that would probably not be needed in a mundane local cell call?

Just wondering... 

Do you think I am right about what's driving these numbers?