The main reason I think people don't do it is because of the possibility of passing diseases around.
I have a male that has been ready to mate since this past spring, but he won't get to mate until 2005. I'd rather wait until one of my females is ready to mate than letting someone else's snake mate with him and possibly contract some disease and die.
If you are a member of a herp club, ask around, I bet someone somewhere is lending a snake to breed it with someone else's snake, but I also bet that those people are close friends and the snakes are known to be completely healthy.
Go ahead and advertise your males, but be aware of the risks and make sure the person who owns the female knows what they are doing. It's also good to write up a written contract so you don't get screwed in the deal. I know someone who lent a male boa to another person and the subsequent babies that were born were sold and the guy who owned the male didn't get a cent from them.
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alstiver@hotmail.com
Current snakes:
1.0 '01 Hypo snow cornsnake (Tesla Coil)
0.1 '02 Ghost (pastel) cornsnake (Banshee)
1.1 '02 Bloodred cornsnakes (Desi and Luci Too)
To be added in Spring:
0.1 '98 Het Hypo, Het Caramel cornsnake
1.0 '00 Hypo Het Caramel cornsnake