The Mystery of the Billboards

On a recent road trip, with nothing better to do, I decided to count and categorize every billboard on my side of the highway for a stretch of interstate the length of one state. I did this on the return trip as well. The total distance of my billboard census was 210 miles, and the total number of billboards was 202. While not representative of billboards nationally, the results do raise disturbing questions. Here is what I saw:

	number	percent
Total billboards	202	100.0%
Land for sale	23	11.4%
Home/office for sale/rent	21	10.4%
Motels	20	9.9%
Outlet malls	20	9.9%
Blank billboards	15	7.4%
Restaurants	12	5.9%
Radio/Internet/television	8	4.0%
Vehicles	8	4.0%
Alcoholic beverages	5	2.5%
Gas or gas/restaurant combos	5	2.5%

The remaining billboards, with one to four in each category, were a hodgepodge that included medical services, churches, events, household furnishings, home improvement, camping/RV, community promotions, exit promotions, antiques, flea markets, military recruitment, public health, service organizations, department stores, clothing, lawn and garden supplies, insurance, banks, boats, docks, food products, and museums.

Observations: 

1) Most billboards looked faded and yellowed. Did the business still exist? 

2) Most billboards were difficult to read. Few communicated their brand.
3) Of the 20 billboards for outlet malls, 19 were for a single mall.
4) Among the 202 billboards, only 6 were digital.

Questions:
1) Are GPS devices and smart phones undermining the billboard industry?
2) Why are so many billboards selling things that nobody wants? Is this an advertising medium of last resort? One in five billboards was selling real estate in one form or another. A large proportion of billboards were blanks or advertising their own space.
3) Is the sorry state of billboards an indicator of a crippled economy, the slow descent of portions of America into third-world status? Are rural stretches of the United States hollowing out, leaving the lamest businesses behind as creativity and gumption move to urban centers?

Just asking.