In a continuing effort to improve AddThis, we have decided to move it to a new platform. With new requirements to reliably deliver the widget over 200 times per second (yep, you read that right), this was only a matter of time.
So during the next few days you will start noticing significant improvements in the speed of delivery of the AddThis Widget. The delivery will also be more reliable as the new servers will do load-balancing; if one server becomes overloaded with traffic the others will immediately jump in and take on some of the load. The transition to the new servers will happen completely seamlessly.