Yes Richard. I'd be more worried about using for exit nodes in China and Russia. A Russian node was seen to be modifying updates downloaded through Microsoft's website. The NSA has and is actively trying to deanonymize tor users. I doubt they can be identified by name or IP address. They can just buy some IPs from any ISP or hosting company.

There is no way to access them if they go down. Some servers after offline but come back for various reasons.