I have been asked by our tour guide found on trip advisor to provide my passport number to him by email as one more piece of information he needed after we had already reserved the trip. He said its a new requirement by the Greece government. I've looked online and can't verify. Is there any dangers to giving out your passport number?
I don't see any danger. A lot of tour companies do it. For example when you arrive in hotel you are not delayed at the reception and go straight to your room because they already have all needed information.
jackie, The Greek Travel Agency that I dealt with on my last trip asked for not only the number but a copy of the information page of my Passport. I was somewhat apprehensive about this at first, but apparently this is a common practice. I provided the requested information, and haven't had any problems at all. I was really pleased with the service they provided, and would have no hesitation in providing the same information on future trips. Happy travels!