SPF in market place

It means the seller/buyer is making the seller/buyer jump through hoops and not use PayPal like a normal person.

Not always. I will mark an item as SPFs if the buyer tells me they will take it, even when they pay PayPal. Sometimes it takes a minute. Has happened to me, for whatever reason I don’t / can’t pay on the spot and promise to pay shortly. 
 
It means the seller/buyer is making the seller/buyer jump through hoops and not use PayPal like a normal person.

Not always. I will mark an item as SPFs if the buyer tells me they will take it, even when they pay PayPal. Sometimes it takes a minute. Has happened to me, for whatever reason I don’t / can’t pay on the spot and promise to pay shortly.

There are a lot of reasons why an ad is SPF. I usually like seeing that when I contact the seller when I say I want his product because I never send a large amount of money using my phone and would use my computer. I want to make sure i enter in the right amount of zeros and I don't want to fat-finger a button on my phone's smaller screen.
 
Sorry Pool Fellow - that's interesting.

I use SPF for 'sold pending funds' when I've received serious interest from someone and we are in the phase between I'll take it and payment. It indicates to others that the item 'may' be sold. If someone is very interested they may send you a PM to get in line in case the buyer backs out. It also prevents me from getting 20 PMs about an item if I'm in the middle of working out a deal.

I think using SPF shows respect to the buyer in so much they know the deal is secure and you (the seller) isn't some douche just waiting for the highest offer.