What protections are in place for losses? What are you procedures for storing coins (hot wallets, cold wallets, etc)? Do you have a guarantee you are willing to publicly stick by? Has your marketplace been audited and verified by a third party security firm? How often will you undertake auditing of your marketplace to ensure that it remains secure and funds are safe? If customer coins are ever compromised, will you cover 100% of the losses?
I have a few BTC, I would be more than willing to try this out, if you were more forthcoming in regards to security and your guarantees. Being a funded marketplace, I would like to think you built a decent and secure environment for Buttercoin as well as got the site audited independently by a third party security firm who perhaps specialise in financial/marketplace scripts.
I am not trying to be cynical here, Buttercoin looks great, but you can understand given the losses I have endured the past year, that I am very very hesitant to trusting another marketplace and I assume there are many out there like me who have been burnt the last year. My trust in all coin marketplaces has been broken, I just need the public reassurance you will do things differently and your policies/procedures before I move any of my BTC.