I just noticed today that adsense doesn't offer an option to be paid by paypal. It would be a serious convenience iif they did.
On the early days Adsense was launched, it was suggested to get paid via Paypal, but happens that being a Google brand, they wanted to own Paypal and, has happened with whatever they can't buy, Google decide to launch their own payments processor under the name of Google Wallet, that has been so unsuccessful as their other "cloned" versions of sites they cannot own, including Facebook (Google Plus), Twitter (Google Buzz), Yahoo Answers (Google Answers) and so on. However Adsense was limited to pay with checks on the early days, failing to introduce Google Wallet payments, they later added the ability to get paid via bank transfer, which is way too much easier and faster because, if Paypal were possible, money land on the bank at the very end. As for Paypal alternatives, there was already one that was a real contender for them; StormPay, but this payment gateway got into trouble when they began to second HYIP and other dubious schemes that associated them to e-Gold, which was a failure alternative to PayPal as well. Moneybookers seemed to be the next best alternative, but since they switched name to Skrill, they have not succeeded in the attempt to be the option of choice between actual Paypal users. AlertPay was another promising option that was put into question, much in the way it was for StormPay, but while there are many other payments methods aside of these, Paypal remains as the most recognized among all of them, regardless whatever horror story associated to it.
There are lots of alternative, but not a lot of online store use them at this point. I think one reason is that it gets really complicated for companies to work with multiple payment options. It's easier to use an alternative if you are just sending payments to people who will likely just deposit them into a checking account, but as far as doing regular business, it's hard to use other things because most of the customers will want paypal.
