I virtually always ask for payment marked as "gift". I've had a few folks that just put the fees in and send it as goods.
Unless its a blanket listing, I usually charge exact shipping on an item and that's AFTER I've went to the UPS, USPS, and FedEx sites and calculated exact shipping for the packed box. I do that for the buyer's benefit, not mine.
After selling a ton of parts earlier in the year, I calculated how much I paid in PayPal fees and shipping materials (packing tape, bubble wrap, oversized boxes...aren't free) and the amount I paid was stunning.
When you ask people to pay the PayPal fees, many get offended and act as this is my cost of doing business. Frankly, PayPal gives the buyer protections and the seller absolutely NONE. There is no benefit and I'd rather use good old-fashioned money orders. I've been scammed twice now from buyers that requested that I send items regular USPS mail. I've had two claims made from buyers saying that I never shipped. I can't provide tracking for regular mail, so PayPal automatically sides with the buyer and deducts the funds from me. Neither were huge, but getting scammed for any amount is very frustrating.
And, oh by the way, to those that reply "just pay for tracking" that not only increases my shipping costs but it doesn't prevent the same issue with PayPal from occurring. I shipped three working vector boards to an eBay buyer last year via FedEx Home Delivery with tracking. Buyer said I sent an empty box. I provided tracking information showing delivery WITH the verified package weight of 10 lbs (doesn't seem empty to me) and PayPal STILL sided with the buyer as I couldn't prove the items were there.
As you can see, I'm not a PayPal fan.
Scams used to be less frequent, but with a bad economy it seems more people are reverting to this. Buying or selling is not an ironclad transaction any longer.