> I was thinking about it, and I prefer to have a default profile (I can build just fine without passing any profile, and it picks up 2.9). 

Unfortunately, that is not possible. Even with the current setup you always need to pass a profile (as you can see here https://github.com/scala-ide/scala-ide/blob/master/build-all.sh#L13).

> The Scala worksheet is a pain to build for exactly this reason.

The problem is maven, which doesn't allow a profile to enable other ones. The solution for reducing the pain with this is creating a script, just like we do in the Scala IDE.

> We should strive to eliminate all barriers for new contributors, and being able to "just build" is the first step.

The only reason why I was against having a default is that we may have assumed it (for instance, when setting up a Jenkins job), and hence changing the default can have bad side-effects.

But, I agree we should do all we can for lowering the barrier for new contributors, so I'm ok with having a default. http://scala-ide.org/docs/dev/setup/setup.html should be updated accordingly.