Bear in mind that some guys get fisted, or play with very large toys. I have a friend that takes toys measuring 13 inches around, and is working up to bigger. An ass that has been well-worked with a big dick, fist, or toy will not just show an open hole (like the picture I think you are refering to), but will be swollen, and have the sphincter pulled out, like a rosebud. During fucking, you will see it pull out like lips, following the dick as it is being withdrawn.
While I don't take anything up the back, I've had my bottoms tell me that getting fisted, or taking a big toy, is a completely different experience from getting stretched fucked with a thick dick. Some tell me that my dick hurts them, although I see them take an arm obviously much bigger.
Not everyone's ass reacts in the same way. Some guys stay very loose permanently as a result of their ass play. Other guys tighten up between sessions, but open up loose after a little fucking. A few seem to be amazingly elastic, and can tighten up quickly after anything.
I once met a guy in the back of a bar, who after feeling my dick, wanted me to fuck him, right there in the bar, right in front of his husband, who was also there. (whatever turns you on...) So, I bent him over a bar stool, and proceeded to give him a good pounding. He had the sort of ass that just opened up wide and loose after a while. While I'm doing this, the husband is getting horny as hell, and is furiously jerking his dick, which is barely average, and fairly thin. Every once in a while, I'd pull out, and give the guy a 30 second breather. A couple of tiimes, the husband was just overcome, and jumped on the guy's ass when I pulled out. But the way that hole was stretched out, his dick must have been lost in there.
