Luckily, everyone on my list are people that I wouldn't mind visiting me whenever. But it has crossed my mind at one point -- what if I didn't want that person to follow me?
I feel that having to accept/deny a follow could work, but it would create two issues: 1) Having to deal with rejection of a player TPing to you (which might cause drama/hurt feelings, and I know I'd personally be pressured to say yes anyway to avoid that.) and 2) If you have multiple friends are massfollowing you, I.E onto a boat, it would be annoying to hit "yes" repeatedly.
Thus, the type of TP system I'd wish for is a toggle of some sort -- an on/off switch. If it's off, players can't follow you, but they can when it's on. I'd just turn it on when I would be okay with someone TPing to me.
Of course, I then can't decide WHO I want to visit me, but if I'm really against that player coming to see me, I might as well delete them. I dunno, perhaps both systems would be nice (and the option to turn off the accept/deny prompts).