This works:
\setupinteraction[
color=blue,
contrastcolor=red,
focus=standard,
state=start,
]
%\setupbackend[export=yes,xhtml=yes,css=yes]
\useURL
[UUID]
[
http://en.wikipedia.org/wiki/Uuid]
[]
[universally unique identifier]
\starttext
This new id is generated much like an \from[UUID]. The reason for the
change was that in this way a client number could be generated offline
and/or different databases could be merged without the risk that id's
would clash.
\stoptext
But when the \setupbackend is taken out of comment, it goes wrong.