Best system I've seen is with WebMoney, where user have reputation score based on their activity amount, users can write about problems in their profile (and account owner can answer publicly) and you can set yourself what information is public and what is private. For example, here's account that Valve (and others) use to process payments: http://passport.wmtransfer.com/asp/certview.asp?wmid=362311291686 . It has a high business level, has been verified and ok'd to have real info via notarized documents (but still the actual information can be private) and complaints are public. This gives the option to the user to decide if he trusts the other party or not.
Maybe it's a cultural thing too, but both Europe and Russia have a history that makes people understand how important it can be protect your private information. PayPal system is really limited compared to WebMoney, but sadly it's only used mostly in Russia and other CIS countries.
However, such thing is much harder thing to pull out with other services like Moneybookers, WebMoney, Liberty Reserve and the now-gone ePassporte (and various others). All transactions are final, so it doesn't screw up the seller. That's why sometimes merchant require buyers to wait several days to get their digital goods or services if they're paying with PayPal.
Another thing about PayPal really are the fees. They might be ok for single purchases, but they stand to go really high if you take in lots of money, or for example get your payments via PayPal. This is especially true if you work with something like affiliate marketing and the companies pay their commissions via PayPal to international affiliates. If you generate the normal wage amount of commissions, lets say $3000 a month, the fees take $100-200 out of that. Other payment options do not take that much. For example ePassporte took $0.30 per transaction. That's why I generally use other services than PayPal, but sellers most likely have to use it as sadly PayPal gained the marketshare in western world, especially US.
Fair point about the DRM... I also like the fact you get extra Steam/Desura keys for the bonus games if you paid more than average. Gave those to my sister every time and she was happy.
Aaaand that was illegal. It clearly states they're only for your own use.
On top of that, Linux is a support nightmare. The drivers are horrible, the system underneath is a moving target that changes A LOT between different Linux distros and with multiplayer games Linux users would cry aloud about some anti-cheat software like PunkBuster, VAC or Blizzard's one scanning their system while playing.
There's also no good distribution platform for Linux, like Steam. And no, apt-get or yum won't work. Considering all these, it's just not worth the effort.