El Reg notes that PayPal is losing market share.
Reasons given: being tied up with eBay, and poor marketing.
Reason not noted: politics.
PayPal's mission statement, as noted in the article: "PayPal is the faster, safer way to pay and get paid online."
It turns out that there's fine print. A lot of fine print. Well hidden (starting from the main page, I couldn't find so much as a suggestion that PayPal was anything less than a secure way to transfer funds).
You see, PayPal is a funny sort of bank. (Sorry, not-a-bank, as it insists that banking regulations don't apply to it.) It only allows commerce that's acceptable to California politicians.
The one specific restriction that I've heard of - and I expect there are many more - is that PayPal may absolutely not be used to pay for anything even remotely connected to firearms or accessories, however legal the transaction.
I've had credit cards from a variety of banks over the years, and, while I've occasionally had issues with making payments to, e.g., a Czech company by way of a Dutch payment processor, I've never heard of a restriction on what type of merchandise I can buy with a credit card. PayPal, though, is different: kind of like having a WCTU affinity credit card that can't be used to pay for anything related to drinking. Only the WCTU affinity isn't advertised, and it's trying to be the only game in town.
When a payment processing company sets itself up as enforcer of public morals, it becomes less than a payment processing company. And, inevitably, it drives customers away.
If PayPal were a neutral conduit for the transfer of money, there'd be a lot less demand for alternatives. As it is, there are plenty of businesses looking for other options for handling online payments.
(And that's not even getting into the rumored outrageous business practices that PayPal could mostly get away with when it was the only game in town.)