Anybody ever seen it?
Nothing in the archives, however plenty on a main-google.
Appears to function similar to MSSmartTags.
"Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.56 Safari/536.5 SmartLinksAddon"
In addition to visitors IP, requests are replicated from multiple Amazon AWS IP's.