Managing SQL Server Service Accounts

One thing I haven't been sure about is the best way to set up service accounts in SQL Server 2008. I know you should use a unique account for each service (Database Engine, SQL Agent, AS, IS and RS), but I was wondering about multiple instances. Is it a best practice to use a separate set of accounts for each instance, or (for example) should one RS account be used for all the Reporting Services on the machine?

After consulting Books Online (which says, "Run separate SQL Server services under separate Windows accounts.") and reading this editorial and the resulting discussion on SQLServerCentral.com, I decided that each service of each instance should use a unique account. Here's my naming convention:

You can see that I've collected the accounts into a Group named 'SQL Server Accounts', and that they follow this naming convention:

• SQL - so all the SQL Server accounts will be listed together
• Instance Name - 'PJM' in this case
• Account Name - SQL Agent, Database Engine, Analysis Services, Integration Services or Reporting Services