Hi John,
There is no maximum number of concurrent connections on SQL Azure Server defined. In theory it depends on hardware and OS capability. Connection pool is a client side conception, you can define its size in your client application.
I recommend that you use connection pool to connect to your SQL Azure server. In your application, if you set your connection pool's size to 100, it means that concurrently you can have maximum 100 concurrent connections, but if you encounter bottleneck
on the connections, you can increase your connection pool's size. Here are some articles for your reference:
Connection Constraints
http://msdn.microsoft.com/en-us/library/ee336245.aspx#cc
Connection Pooling (ADO.NET)
http://msdn.microsoft.com/en-us/library/bb399543.aspx
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