I’ve just experienced my first unsolicited belly-touching, by a colleague whose pregnancy advice was to drink lots of juice and laugh more. This walking up to me and feeling my bump to see if it moves – is that going to happen a lot? It’s still so gentle that even Pete has only felt it kick once.
I understand people taking an interest in the pregnancy, but I’m not sure that should extend to unsolicited – unauthorised, even – physical contact. And I’m not brave enough to respond by touching the feeler’s belly in return. I wouldn’t be so rude!

I’d wager that the belly touching is just going to increase as the belly does.
Ew… creepy. A suitable deterrent might be to yelp, as if they’ve given you a small electric shock. And then start chanting.
They’ll be in another room before you know it.
I tend to think it’s the height of bad manners to touch someone’s bump without asking.
Much like stroking someone’s hair without asking.
It’s just creepy and wrong.
Being interested is fine, but being hands-on interested is not.
How you deal with it will, I suppose, depend on the person, but moving away or asking them not to touch is probably the least likely to cause offence. I’d hope.
Yes…it’s as if everyone in the world feels some sort of cosmic connection to the bump. Just wait until the baby is really obvious…complete strangers will come up and talk to it and touch you. It’s just icky.
I agree touching their belly in return is a bit much. How about a smack in the face?!
Invasive and vile. Uttering a sharp yip mostly worked for me. But I usually let people who asked (and I knew well) have a fondle. As it were.