At this time we do not support OCS 2007 R2 or Lync Server 2010 with databases on SQL 2008 R2. I am sharing this because this is a fairly common question we receive and we point people back to the documentation on what we do support. The absence of something should always be presumed to be not supported.
If you or your customer are blocked on this then the only process available is to work through the support organization to enter a design change request or supportability request and what the impact of not supporting this will have to your organization.
Because this is something not currently supported, there isn’t much more to share but use the contact form as necessary.
Edit May 9, 2011 - Lync Server 2010 now supports SQL 2008 R2 - http://blogs.technet.com/b/nexthop/archive/2011/04/20/lync-server-2010-support-for-sql-2008-r2.aspx
Edit February 10, 2011 – The testing of Lync Server 2010 with SQL 2008 R2 has been added to the schedule for testing with a rough eta of end of calendar year.
Edit November 10 - There is no ETA for supporting SQL 2008 R2. Do not take the next statement as a promise but simply as what is likely to happen. When Microsoft has to invest the testing resources for a currently unsupported topology they will invest in the most recent product release. This means if and when a statment were to be made, it would be for the Lync product before it would be for R2 and it is possible that it would never be done for R2. So for those customers with R2 or planning on Lync Server 2010, you should work with your Account Manager (for those having premier contracts) and support. The only issue is that support charges to help you and isn't really setup to take product input outside of a charged call. You can use the contact form here as well as the forums - http://social.technet.microsoft.com/Forums/en-US/ocsplanningdeployment/threads