I am not affiliated with Linkworth. I used their service before. But I came across this posting, and I thought it is weird that Text-Link-Ads bought their competitor's keywords (Linkworth).
If it's relevant then there would be no reason not to buy a competitor's keyword. While the trademark rules under Google can prevent advertisers using the keywords in advert text (which hasn't happened in this case) there are no longer any rules in the UK or USA/Canada stopping people advertising under competitor keywords. In some cases you can get some very good results using competitor names as keywords...