Paid Advertisers, Do you include a few (or less) broad/phrase match keywords in your adgroups, just so that can attain new keyword ideas? How often do you inspect your search query report and extrapolate good keywords and negative matches to include in your adgroups/campaigns?
I usually include a few broad match keywords in an account to catch and later include long tail keywords. It is difficult to think of long tail KW's sometimes and this is a great way to find them. I suggest reviewing the SQR every few days to find new keywords as well as find negative keywords to add to your account. If you use broad match keywords you will absolutely find yourself adding negative keywords. i.e. broad match keyword: mold inspection could cause your ads to appear for "free mold inspection" adding a negative keyword -free will eliminate your ads from being served when the term 'free' is included.
Broad match keywords are good for one purpose...getting you maximum traffic exposure on your ad netowrk of choice. They can also become a very pricey proposition, if, as KimClink says, you don't keep a vigilant eye on the exact searched phrases which brought you the visit(s). Keep an eye on these and update your Negative keywords at least every 3/4 days until you feel comfortable with your keyword library. You could also consider a Phrase match setting to minimize some of the fluff Broad match sends your way.