There has been a lot of writing about the real world intruding into the virtual world of late. The majority of writers on the subject, including James' State of Play write up, Richard's many comments about wanting different rules and laws in "play" spaces, and Ted's State of Play paper take, to varying degrees, the positions that real-world intrusion into online games/worlds is a Bad Thing, that the developers have a choice about allowing it, and that players generally don't want it.
I disagree with those positions.
Appropriately, my State of Play paper is an extensive look at these issues. Its focus is on the requirements for creating Stephenson's Metaverse and it uses examples and data from Second Life and other products. I've been referencing small pieces of it in various comments but comments are often lost, plus the paper as a whole provides a far better look at the issues than a short post possibly could. But, briefly, my thoughts on those positions are as follows.
"Players don't want their worlds commodified"
While there are clearly some who don't, including Richard, Ted, Sony Online Entertainment's General Counsel, and most game developers, the volume of transactions on eBay and the popularity of alternate options that appeared after the EverQuest ban, like PlayerAuctions, indicate that tremendous numbers of the players of MMORPGs have decided that they want to be able to short circuit leveling. There are a lot of them and they are voting with their feet.
"Developers have a choice about this"
I don't think they do -- see the above paragraph. Now, I can think of games that do not have marketable items (Quake and Scrabble come to mind) but the nature of RPGs is that time == more fun. Since not everyone has time, those who are able will change it to money == more fun. Without biometrics (and even with, as Kevin points out) I see this as an extremely difficult problem and a waste of good development resources.
"Letting real-world laws into the virtual world is a Bad Thing"
No it isn't. In fact, the burden of proof lies with those who believe it to be true. Play and fun clearly exist within the place with the most complete implementation of real world laws possible: the real world itself. In Lacrosse you can beat the tar out of someone with a stick -- but if you murder someone you'll still be meeting Officer Loink. This "intrusion" of real world laws doesn't make Lacrosse less fun. It seems to me that online worlds aren't getting enough credit if the application of real world laws somehow ruins them.
In fact, letting real-world laws into virtual worlds is the critical step if online worlds are going to become the Metaverses that many of us want them to be (sorry, but you'll need to read the paper on this one!)