If you are referring to micro-transactions whereby readers pay content authors, tipjoy and others have already tried the "e-tip" model and failed.

Also, paypal's donate feature has existed for some time now but it doesn't seem to be able to replace ads. If anybody could implement the safe, seamless microtransaction model I'd think it'd be paypal as they have the existing infrastructure already. Either they have overlooked it or they've decided that the model wouldn't work.

Paypal? No. I just signed up for an account using my debit card. Instantly, my account is suspicious. They then demand access to my bank accounts and scans of my social security card, birth certificate, photo ID, etc. No thank you.

Many good ideas have to be tried a few times before someone gets them right. Witness Sun's "network computer" ideas in the '90s. As far as I can tell Flattr is doing well and gradually growing.