Hmmm. My experience is that the sort-choice remains until I manually reset it (perhaps for a different "shelf.")
Hope Shelfari addresses your question.
Hi Ellen--The shelf sort is "sticky" so however you chose to sort your shelf last is how it will sort the next time you view your shelf or another member's shelf. The only reason I can think of why this wouldn't stick is if you have the cookies for Shelfari on your browser disabled.
Thanks for your response. My shelf used to sort the way I left it (by author) but it no longer does. I checked my browser preferences and cookies are enabled "only for sites you navigate to." I DO navigate to Shelfari, which means cookies should be enabled. I manually reset my shelf to sort by author each time I visit. I have no idea why this doesn't stick.