People are referred to on Espra Trustmap using contextual identifiers. These identify the user in a particular context. The simplest (and potentially the only syntax you need) is @username, which identifies username on Twitter. For example, @thruflo is http://twitter.com/thruflo.
With the @username syntax, the "@" symbol is the context and "username" the identifier. This is shorthand for the fuller syntax: ~twitter:thruflo (which is equivalent to @thruflo) where "~twitter" is the context and "thruflo" is the identifier.
One common tricky case is refering to a Facebook user who hasn't setup a username. The trick is to copy the uid from their profile URL, e.g.: if you're on http://www.facebook.com/profile.php?id=564391013, copy the id=564391013 to make the identifier ~facebook:564391013
We currently support the following contextual identifiers:
@username
~twitter:username
~facebook:username
~facebook:uid
Flickr
~flickr:username
~flickr:nsid
Delicious
~delicious:username
YouTube
~youtube:username
Examples
The following all identify me:
@thruflo
~twitter:thruflo
~facebook:thruflo
~facebook:670325802
~flickr:thruflo
~flickr:13872483@N08
~delicious:thruflo
~youtube:thruflo
We plan to add support for more services and email addresses in the near future. If you have any suggestions, please let us know.