There's a very longstanding bug/confusion in Maven that results from reporting plugins that fork executions. That's not the same thing as forking a jvm, it's an internal maven business where a plugin says, 'whoops, to run me you have to make a whole new maven and run all this other stuff first'.
The cobertura plugin does this. So does Javadoc in some really irritating cases. If folks would like a faster site build, I'd suggest moving cobertura to a profile. If the current 'go for coffee' situation doesn't bother anyone too much, we can leave it alone.
