I agree completely. A lot of hosts do intensive background checks on their guests whenever they get an inquiry, and will decline you immediately if they see something suspicious. That's why it is strongly recommended that you give all the information neccesary to make a booking. I once hosted the owner of HackerHomes on Airbnb, he makes a living by renting out his listings, and one of his main sources of income is Airbnb. He shared his story with me about how he did a background check on this one guest, and found out that there was a warrent for his arrest. I have met another Airbnb host who found out that a guest that she hosted was involved in cyber crimes. There are stories all around of guests like these, so a lot of hosts will have a hard time accepting your inquiry if you do not provide any neccesary details for a background check.
I understand completely that it is scary to give personal information online, but here are a few points that show how strong Airbnb security is.
1.) Airbnb takes security very seriously. As a host, I am unable to get the details of my guests until they make a booking. The only details I see about my guests are their first name, picture, country, and state. The personal details such as passport, age, etc are hidden.
2.) There is no way to search for a guest's name. The only way to find a guest is to look at a listing's reviews, and see the profile of the guest. Again, the profile will only give the first name, picture, country, and state.
3.) The only person who will eventually have access to your information is your host. So if they do something fishy, there will be an obvious cyber trail.
In my opinion, you don't have anything to worry about. Airbnb would not be a 30 Billion dollar industry if they didn't take care of the private information that the guests provide.
Hope this helps!