>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 real reason is that the entire commerce system is evil and only out to screw with your money.

Same here. Time was when I withdrew from an ATM and the balance shown was of that day. Now I see the deduction as of that xaction on the screen straight away. No matter which way I pay my credit card bill: phone, web, cheque in bank branch, post, they all state that up to 4 days are required for it to clear.