sounds like a really good idea but I think in the long run people might not trust you company as much if you mislead them to get to the site. I think what it comes down is to morals and how much you care for what you are working on
I will say this.. It is dumb not to have a url that goes to your site. A percentage of people will type your url in and not click on your ad. Not having it there costs you money. Will that be off-set by some catchy keyword that goes nowhere? Perhaps, but it is only a matter of time before google de-activates your ad for that.
I was thinking more about adding a simple keyword to the end of my disply url, maybe just being lazy and should crete a few more ads. www.OnlineMarketing.com/(keyword)