We have used Loopnet many times in the past to list our commercial properties for sale. As far as listings, they are a good source for commercial listings. However; I've been going around with them lately because there's an agent in San Clemente that is advertising properties that aren't his. Not only are they not his listings, he knows that they were foreclosed on and sold, and he continues to advertise them. When I called the broker he told me to send in an offer. When asked if they were listed and if he had authority to represent them (I knew they had already been sold from researching them) he skated around, saying I could send him an offer.
I notified Loopnet a few times, and also emailed the broker telling him he should take the ad down. They're still on there, under the street Chula Vista.
It's the only time I've had a problem with anything listed on Loopnet.