I posted a few weeks back about how there is no good reason to disable IPv6 on SBS 2008 and how I was pretty sure that you should not do the same on SBS 2011 either. Well Microsoft’s SBS support team have posted that indeed you should not do it. Their blog post here lists some of the problems that can be had if you disable IPv6 on SBS 2011. They also show how to disable it correctly if you have to do it.
I’m yet to have anyone give me a reason as to why you should disable it on either SBS 2008 or SBS 2011.