I have to be honest I do tend to be very aggressive when it comes to brand bidding. This is something that recently came up for legal Review in the Interflora v Marks & Spencers legal case.
I do tend to find competitors bidding on companies that I represent for example they bid on "oakfurnitureland" which is fine, they have to realise though that if they play with fire you get burnt.
If they do this I then go after every search term that drives traffic to their site. I feel a bit like Gary Oldman in the scene from Leon, bid on everything, EVERYTHING! Well not quite but you get my drift, in case you cannot remember here is the scene:-
So generally I would warn companies against going up against big competitors that closely watch the internet.