As a business, setting up a public marketplace is about the marketplace, not about the policing. Policing is secondary -- way secondary. There's zero profit in policing the marketplace for Google. There's simply no money to be made. None, until it becomes so rampant that developers like you stop using the marketplace as a result.
There is lots of money to be made in policing the market. Apple polices the its own App Store and it is much more successful than Google's.
Developers want a market so that makes their app easily discovered and their copyright will be protected. If they don't get this, they will focus more resources on iPhone development.
Customers want high quality apps without worrying about filtering through spam and malware. If they don't like the experience, they will buy an iPhone.
The only people who benefit from Google's hands off approach are spammers and criminals. Apple's approach maybe overreaching, but it benefits high quality developers and that is where they will flock until Google gets it's act together.