While I know everybody here already knows this (like someone said in another thread, this ain't FatWallet) the fees ($5 + 3%, IIRC) are the least of your issues with cash advances- the interest (and I've yet to see < 19% p.a.) starts accruing the nanosecond you have the cash in your hot little hands, and continues to do so(do AmEx credit cards use two-cycle billing?) until it's paid in full.

I have PINs set on my credit cards just in case, but ONLY expect to use them if I need bail money or owe money to the Mafia.