A RS-recommended B&B requested my passport number and expiration date when I requested to book a room (in addition to payment and other info). I am wary to disclose that info. Is that a common (and safe) practice? Thanks!
I'ts a little unusual but I don't see anything wrong with that. There's nothing a thief can do with that information since it's not connected to any credit card. If they ask for that instead of a credit card number I'd feel OK about it. You might try looking for red flags in the hotel's reviews over on tripadvisor.com.
Once you're IN Europe, it's common practice for hotel to ask for your passport and copy your info. So, I'm not sure there's any harm in them asking for it first.
They're probably only doing what they're required to do by local laws. Some countries - I think Italy for one - require that hotels register foreign guests with the local police. What's a bit unusual in your case is that they're asking for your passport info in advance. Usually it's requested at time of check-in. In any case, I wouldn't worry.
The others are correct, you'll be handing over your passport when you arrive anyway so they can record the info, so doing it now by email is not an issue. In the old days, hotels used to keep them overnight. It freaked many an American out...
From talking with the manager of a hotel in Spain last fall, I understand that each establishment is required to copy and forward to the local "authorities" the passport or other indentification of each guest. Failure to do so would result in trouble for the offending party. In fact, he advised that on one evening, the local police came to the hotel and arrested a guest based on the information. So, providing the same information on the reservation confirmation would be no different in my opinion. Just a means of identification.