In the UK at least, PIN-challenges for contactless payment are random. I've heard it's supposedly approx 1 in 10 payments require the PIN, but I've been using contactless payment for just over 6 months, and it hasn't asked once (I've also used it a few times in mainland Europe, again, no PIN needed).

Sadly in France for any transaction over 20EUR you have to use the chip. I know that in several other countries you only need the PIN.

Apparently this actually depends on the terminal configuration so I hope that once Apple Pay comes here it will not suffer from the same useless limitation.