I heard a classic example of using a domain that sounds like a generic word but is spelled another way and used on the radio, bad idea IMHO!!
The radio ad was for a new Australian business directory company called Bloo www.Bloo.com.au.
At the end of their ad spousing all of their great features and benefits they gave out the web address just as it sounds BLUE, they did not give the alternate spelling of BLOO to the listeners. Big mistake in my book! If they owned www.Blue.com.au and it redirected to www.bloo.com.au then that would be fine, but they don’t it just goes to a dead page.
So if you are going to run radio ads make sure you have the right combo of domains to cover yourself and if it is a different spelling make sure you let the listeners know how to spell it so they can at least find you.