Sending passport info over the internet

To whom and for what purpose? If you're sending it to a 12 story building in Shanghai's northern suburb of Gaoqiao, it may not be such a good idea. I've had hotels ask to see my passport before, and that's fine, especially if they're required by law to copy down your passport number. I've never been asked to leave my passport anywhere, and I've never had anyone ask me to send a copy in advance. Not sure I would do that...not likely anyway. I have sent a separate photo before when renting apartments but only after both parties have been able to confirm a safe and legitimate deal through a third party booking service (and asked for a photo in return). In this example, the purpose of the photo is to ID the owner/renter when meeting at a pre-arranged location on arrival, such as at a metro station.

Josey, I had to do that on one occasion on a trip to Greece, and was a bit nervous about it. I sent the information, and so far haven't had any problems. The Passport I used on that occasion has now expired anyway. Cheers!

No.

There really is very little information on a photo copy of a passport. Name, picture, no home address, no SS number, etc. Send it. It is commonly requested and done.

This is a bit off topic but to aid in getting a replacement passport in case of a lost or stolen passport email yourself a color copy of the main page and any visas you currently have (also other ID such as drivers license). I also carry color copies with me. Be sure it is a web based email account that you can access from any internet connection. Bringing a color copy to the consulate or embassy is better than a black and white copy.

Josey , as others have said, there not much use with it, your photo and name, they can get that off facebook ,,lol don't worry about it. Its actually becoming more and more common for B@B and apartment owners to request advance scans of passports now. Hotels in some countries are required to look at your passport , and copy out info off of it.
I think Americans worry too much about it.

Its not usual for hotels to ask to see it in advance, but for apartment rentals. Hotels most often have your credit card info on file( in case you cancel last minute so they can cover first night) but aparmtments and b@bs have no resourse at all, maybe they figure at least with your pp info you are less likely to just not show up.
As for what is norm, in some countries hotel owners are required to ask for your passport information by law.It used to be like that in France but apparently not anymore, but I have heard it is still on the books in Italy.