I sent Shutterfly an email as well, and told them I was looking at other printers who offer 10x10, but that I'd rather wait for Shutterfly to offer it. Here's the response I got:
Dear Shutterfly customer,
Thank you for contacting Shutterfly.
We do understand your concern. Currently we do not offer a 10x10 size Photo book. We are considering this as a suggestion from you and we have passed this along to the concerned department for their review. We do take suggestions from our customers very seriously and are grateful for your insights.
Click on the link below to check out the Photo book sizes available at Shutterfly:
Photo Books, Photo Albums, Create a Photo Book, Personalized Photo Album | Shutterfly
Please let us know if we can offer any additional assistance.
Sincerely,
Durga S.
Shutterfly Customer Service
customerservice@cs.shutterfly.com