Is this someone trying to sell a keyword? That if a keyword is queried then your site would come up? That is not good it's a waste of money. The companies that do this use pushy marketing. and basically lie about the users who have the software that your placement will occur on. They have called me several times. It's basically like a kazaa search or similar software that they try to sell you positions based on keywords in the address bar. Good site optimization achieves the same results for less money
I have not joined Towersearch but I see an obvious problem with their service -- they receive little traffic. I performed a nember of searches using my main keywords and many of the results had no listings. Towersearch charges $29.95 per month for 100 keywords. I doubt anyone will receive many clicks. At least with a second or third tier PPC engine you can put up $25, bid $0.01 per click, and eventually receive 2,500 clicks (albeit of poor quality or even fraudulant).