well, guys, it wasn't THEman, it was me.

First, there is one class of RG-59 that usually does not get used for cameras: the old type made for antenna use. It has an aluminum foil and braid, so it is a bit of a pin to get into a BNC connector, and you can't solder it to an RCA plug.

Use 59 for camera because everybody does and it won't confuse anybody. Use 59 because the connectors are available in lots of different styles, including solder, which you can't with the aluminum braid of RG-6.

Use RG-6 when your camera run goes more than, say a couple thousand feet. Use RG-11 (the 1/2" thick cable company cable) if you need to go a few miles.

Here are the reasons you CAN'T use RG-6 for camera signals:
1.that's what they told me in my two-hour CCTV class.
2.we don't have any.
3.the camera guy said so, so I (the cable guy) cannot possibly steal any of his work, even the part he left undone.
4.my BNCs won't fit on the wire, so the wire must be wrong. My BNCs are made for RG-59.

It is basically a case of simple ignorance, where the fact that RG-59 is usually what is used for cameras turns into the rule that it has to be what is used for cameras.

On the REAL side, the only drawbacks to RG-6 are:
1.used to was, BNC connectors were not available for it
2.buying RG-6 BNC connectors may be an unsound investment; I don't know if the same $60 crimping tool that will crimp an RG-59 BNC will also crimp an RG-6 BNC. If I had to spend money on a crimping tool to put on only two BNCs this YEAR, i might also say "you can't."
3.ditto for RCA connectors, although Calrad here in Los Angeles (www.calrad.com, wholesale only, but available at lots of independent retail supply houses) is developing a series of crimp-ons including f, RCA and BNC for RG-59 and RG-6.
4.For those doing the occasional RCA for camera, soldering still is a great idea. You can't solder RG-6 because it has aluminum braid and/or drain wires. It is also too thick to push into the back of most RCA connectors. RG-59 has copper braid, so you can solder to it.