It's awesome to hear that you're building a Scala application that uses Spring Social. You're probably not the first to do this, but you are certainly the first I've heard of.
To answer your question, Spring Social has not been built nor tested against any version of Scala. Although it'd be great to know that it works with Scala, Scala-compatibility isn't really a high priority for the project at this time. But if there's anyone in the community who has had success working with Spring Social and Scala, then I'd love to hear about it.
Looking at your stack trace, I don't see any evidence that the exception you get has anything to do with Spring Social. It might, but there's nothing in that stack trace that tells me that. What makes you think that Spring Social is the issue?
Spring Social Project Lead