Microsoft has documented certain things as part of their Open Specification. This includes SharePoint, like MS-UPSSDSP (PDF) which is documented as
Specifies the User Profile Social Data Stored Procedure protocol, to allow create, read, update and delete operations on social metadata stored in a social data store on a site.
Back in SharePoint 2007, the rule was to never, EVER read directly from the database (with the exception from WSS_Logging). But now that stuff is officially documented specifically with the intent to
help[s] developers create innovative solutions by providing open access to quality technical specifications and support through forums, events, and complimentary technical assistance., I wonder if it's safe to make read-only database calls to the SharePoint databases now, especially given the poor feature set of SharePoint 2010's Social Features through the object model and web services?