Cell phones
I also go with Gordy's statement.
Especially in densely populated area's, cell sizes are small, and from any high your phone may adress too many cells simulateously, kind of short circuiting the supposedly different frequencies, reducing effctive capacity as a result.
The operators dont like that.
Solution: fly low and slow if you do want to use it.
In less populated areas cell size are bigger so problem does not occur.
If it were so dangeraous, I really would start worrying about all the fixed ground station antennas around....
d3