Trulia guy/lady is right. Your assessment is pretty cynical, and inaccurate. Zillow has a higher volume of fraudulent listings because as of March, it had nearly 2x the market share of Trulia, and a whopping 14x that of Redfin. The listing quality teams work really hard to tear down scams as quickly as possible, but understand that as with any content flagged by users, your report enters a queue and has to be evaluated by a human before any action is taken.
Zillow, like Trulia, also invests a lot in developing their product to prevent, detect, and remove scam listings. To not do so would make the product unviable.
Popular sites are locked into a constant arms race with people seeking to defraud other people. Everyone's gotta make a buck somehow, and fraud is just the unfortunate dark underbelly of commerce.
Edit: Full disclosure—I do work at Zillow, and many of our hackweek projects are also focused on scam detection and prevention. Our objective is to provide the most robust and reliable service to consumers and to connect them with skilled agents, rated by other consumers. In two years I've never seen anyone scoff at a customer complaint or suggest we should ignore something until faced with the threat of "bad PR". I love working at Zillow because, above all, it's full of very decent people. And personally, I'm excited for a potential Zillow/Trulia merger because we all admire them a lot, and we certainly have a lot to learn from each other.