To answer Keith's question..
I will start by saying this...it depends on "who you are" because there are certainly exceptions to contract structure rules in some cases...
OK...this is possibly a "what came first, the chicken or the egg" situation. If the talent was a radio personality first and then landed a TV gig then there most likely would not be a problem...however if the TV talent gets a side radio gig second then there is a potential problem so to speak.
In general, most TV talent contracts prohibit talent from doing paid radio gigs, TV gigs, newspaper, magazine, web columns etc. Under most contracts...TV talent must get permission from the management and ownership to do paid outside projects such as radio and so on.
In TV, the station "owns" your name, face, likeness, voice, blah, blah, blah and the talent cannot shop their "services" because it is (in the stations view)unique and in almost every case, exclusive to the TV station.
Also, there are usually several contract clauses dealing with what is essentially payola...for instance TV talent cannot accept "a gift" from someone that has a value of more than 25 dollars. Of course this does not apply to the talent's family. Again, for instance, talent cannot go to Houstons and have a 100 dollar tab comp'ed...that would be a violation of the contract because there could be an expectation on Houstons part that the talent will mention on the air that "hey...I had a great dinner at Houstons the other night..." in exchange for the free meal.
SO, what it boils down to is...if TV talent is given permission by the TV station to do a side radio show...the TV talent cannot personally voice any commercial or endorse any product in exchange for money or services...doing so violates the original TV contract and violates journalistic and station ethics set forth in the TV contract.
TVGuru