When I first started using Windows 8, I didn't think using a "Microsoft account" to log into my computer was such a good idea (and it probably still isn't) but I gave it a shot just to see what it did. I only planned to use it for a day or two. That was, oh, 180 days ago. The ability to sync my desktop with my other computers is a favorite feature.
However, there is one drawback when you do this: you can't use BCM with a shared BCM database on a SQL Server. BCM uses your windows logon to authenticate you with the BCM database and you can't make a Windows logon on the server that uses the Microsoft account address.
The address I use with the Microsoft account is also the email address for an account in the domain with the SQL server, yet sharing the BCM database with this user doesn't work either (both accounts use the same password).
If you need to access a shared BCM database on SQL server, you can't use a Microsoft account to log into your computer. You'll need to use a local account.
If you are sharing a database between two Windows 8 computers, you can use Microsoft Accounts and share the BCM database. The Microsoft Account authenticates correctly, since both computers are using the same account. Only shared databases on a SQL server is affected.