add a note in the api guide

Author: Alexandru Scvortov

docs/wikipages/data.ApiOverview.txt

@@ -134,6 +134,11 @@ The following two code snippets connect to an AMQP broker:
  factory.Uri = "amqp://user:pass@hostName:port/vhost";
  IConnection conn = factory.CreateConnection();
 
+Since the .NET client uses a stricter interpretation of the AMQP URI
+spec than the other clients, care must be taken when using URIs.  In
+particular, the host part must not be omitted and virtual hosts with
+empty names are not addressable.
+
 All factory properties have default values. The default value for a property will be used if the property remains unassigned prior to creating a connection:
  - username: [code "guest"]
  - password: [code "guest"]