As an example let's tag this WikiPage with a DiiGo or TrailFire tag (other tagging systems welcome)
tag = "VirtualTwinPage"
Then any wikipage T1 of some wiki W1 in the web, that contributes to this notion, tagged by "VirtualTwinPage", is indeed a VirtualTwinPage to W2="MeatballWiki". It needs not necessarily have exact the same title, but it should contribute to this topic.
Virtual twinning allows easier making of StrongLinks. We only need to leave a bottom line, as practised on this page and on TwinPage.
This fosters AccidentalLinking.
The main advantage of social annotation systems is their capability to heal the Web from its chronic weakness of not having implemented StrongLinks from the start on. "The current Web suffers from WeakLinks?". "The current Web's weakness is caused by being based on WeakLinks?." "The current Web's weakness is exploited by a multi billion dollar industry".