This functionality is absolutely crucial for me. I've just mentioned this in the Marvin thread
Competition is a good thing. I know the ShuBook developer is a hard-working and forthcoming person. Let him know that a competing app like Marvin is capable of exporting bookmarks, highlights and annotations with a touch of a button. And you can also restore them with a touch of a button later on, even if you deleted the book in the meantime. You can also send your highlights and annotations to another Marvin user, who can then load them in his/her own copy of the same book.
Good luck communicating these needs to Apple or Amazon. They will ignore you, because they're not really interested in customer feedback. I know that the ShuBook developer is different. Right now, Marvin is the only e-reader app (as far as I'm aware) that allows you to do what you wish to accomplish with highlights/annotations.
If ShuBook also develops this feature, so much the better! The two apps can inspire each other, each trying to excel. For example, I recommended to the Marvin developer to imitate, if possible, the wealth of OPDS catalogue options offered by ShuBook. In no other e-reader app have I seen the OPDS feature laid out so well as in ShuBook.