Ah. I was assuming that it was a situation like Ford buying AdWords for "Chevrolet". If it is more like Speedy Plumbing buying AdWords for "snake" and "plumbing" when your business is named Snake Plumbing, then I don't think you have much of a trademark case there.
In that case, businesses exist that can help your business search for and monitor more defensible trademarks. If you are truly hurt by competitors buying AdWords, you really should thrust your hand into the fire and suffer the pain of rebranding now, because it's only going to get worse the longer you wait. Switching from "Snake Plumbing" to "Jessaustin Pipewranglers" would hurt temporarily as you trained your existing customer base to use the new name, but uncommon or newly coined words are so much more defensible.
In that case, businesses exist that can help your business search for and monitor more defensible trademarks. If you are truly hurt by competitors buying AdWords, you really should thrust your hand into the fire and suffer the pain of rebranding now, because it's only going to get worse the longer you wait. Switching from "Snake Plumbing" to "Jessaustin Pipewranglers" would hurt temporarily as you trained your existing customer base to use the new name, but uncommon or newly coined words are so much more defensible.