>When I charge something against my bank card, debit or credit, my available account balance almost immediately reflects that amount. When I have money tranferred into my bank account, PayPal or a refund on a purchase, I usually will not see anything regarding that transaction from 4 to 10 days. Why is that? It makes me feel that the entire commerce system is evil and only out to screw with my money.

When you initiate transaction it immediately affects your account. To be precise, credit card purchase will be treated as 'pending' for 1-2 days, i.e. you may see it, but it is not debited yet. When you are on receiving side of the transaction, e.g. expecting a transfer, money will appear only when transaction is authorized and completed, i.e. it is the same 'pending' status for 1-2 days, but on the opposite side of the transaction.