I cannot talk for everyone, but I use paypal instead of Google Wallet, because it allows me to pay without using credit card. I do think that current model of credit card payment is broken so I refuse to use it. Sure if dishonest merchant purges all my cash from credit card I could get it back by contacting bank, but money lost would be covered by all bank clients. I don't have much trust in paypal, but I can transfer to it appropriate amount of money from bank just before the payment, so possible damage is much lower. That said my level of trust with facebook is so low that I would probably refuse to put on their account even 100 USD.