Just a pondering and maybe someone can shed some light?
Sometimes I look in the Manage Customers section and I see customers who have created an account (from the registration page) but have nothing in their shopping carts and no other real details.
On my registration page there is the Captcha, so I don't think these are bots.
But why do you think people do this?
Did you ever get an answer to this question?
We seem to have a similar problem...
There are actually several reasons. The simplest is that they planned to buy something but either decided not to, or they were distracted and forgot to come back.
Another reason is that it's quite common practice that stores offer discounts for registered users (having as big user base as possible has value of its own and thus stores sometimes offer incentives). People occasionally want to check if it's the case.
I think you should set up extension such as social login that allows your customer to use social account to register. Through social account, you can have a little information about your customer.