The first week or two after the Fire was released the Amazon Silk servers were constantly having problems. I guess they were overwhelmed. At any rate, it was common for Silk to stall out on many websites and not be able to load them at all. Turning off acceleration by-passed the Amazon Silk servers and substantially improved performance. Hopefully Amazon corrected the server issues by now (I haven't checked), but I suspect they still act more as a brake than an accelerator.