Throttling and the standard bindings inside the Indigo CTP allow you to set and control the maximum number of connections coming into the system.  This is only settable on a few of the standard bindings, like NetProfileNamedPipeBinding and NetProfileTcpBinding, however the default value for these is 10.  So if you are using these bindings and expect your web servive to get much activity you should increase the number.

These bindins also play a part in how security works, security sets up a second parallel connections so if you set your MaxConnections to be 1 and try to connect to the service with a secure channel, it will timeout and not connect.

To set the max connections on the bindings is quite easy, you just do this:

NetProfileTcpBinding frog = new NetProfileTcpBinding();
frog.MaxConnections = 30;
To set the MaxConnections on the host when you setup the ServiceHost class you access the Throttling property and set connection inside there.

ServiceHost<MyService> womble = new ServiceHost<MyService>();

womble.Throttling.MaxConnections = 30;
The throttling value for the MaxConnections property defaults to MaxInt, so it is more likely you will see constraints from the binding themselves than you will from the throttling, unless you setup the throttling yourself of course.

Throttling is done at the ServiceModel level of the system while the bindings are actually down at the channel level, so they tend to operate slightly differently than the ServiceHost throttling. The MaxConnections on the service host is also across all the possible endpoints associated with that service, not just the specific one the binding is aimed at.