Like Warren, I know someone who did this very thing and it did work in many instances...until a snag.
I think many companies are unaware of all the options there are in registering a domain name. Many companies, big companies, will hire someone to develop a site and be done with it. In many instances the webmaster who put together and maintains the site is not even an employee of the company or firm represented.
She approached a large US based chemical manufacturer about one of their domain names she owned and it was available for sale. Reasonable price, no blackmailing, very innocent on appearances letter.
She got a certified or registered letter (one of those you have to sign for) for the firm's legal department demanding that she surrender their property at once. She showed me the letter and it was no joke and this was a huge firm and there was really no need to contest it. It was filled with all the legal speak and potential fines and penalties as perscribed by the state and federal courts of law, etc.
I think she mistakenly called their attention to the issue to begin with.
She gave up the name and she don't play that game anymore.
My personal experience involved registering some domains relating to the Academy Awards and the Oscars (same thing). Within a couple of weeks of regging them, similar registered mail showed up for me. They appeared to have a service alerting their legal team to infringement issues as soon as the names were regged.
They outlined, for my benefit, each and every case tried and won in a court of law protecting the rights, trademarks, images, etc. Very pretty and fancy expensive paper from an LA law firm.
Seeing how quickly this showed up, I cancelled each domain regged and forwarded copies to the law firm cancelling the cancelation.
So I never got the chance to barter the names.
It's a crap shoot. It may end up biting you in the butt but hopefully not.