I tell them that I download tons of freebies and don't always take time to check descriptions.
It works where the books are more obscure, with ambiguous titles.
I'm kinda stuck not buying the ones that scream... what an atypically naughty girl I am.
If a book is lendable, I'll borrow for a half/day and hope they don't look in the archives before i disappear it.
So, yes, I too wish there were a way to create collections in the archives (that alone would be awesome) and make certain ones private.