Uses
Ident is important on IRC as a large number of people connect to IRC from a server shared by multiple users, often using a bouncer. Without Ident there would be no way to ban a single user without banning the entire host. The server administrator may also use this information to identify the abusive user.
On most IRC networks, when the server fails to get an Ident response it falls back to the username given by client, but marks it as "not verified", usually by prefixing with a tilde; e.g. ~josh. Some IRC servers even go as far as blocking clients without an ident response, the main reason being that it makes it much harder to connect via an "open proxy" or a system where you have compromised a single account of some form but do not have root (on Unix-like systems, only root can listen for network connections on ports below 1024).
However, Ident is next to ineffective when used with personal computers, on which the user often has enough privileges to make the Ident daemon reply whatever the user wants. In fact, most Ident servers for Windows don't even bother checking the owner of a connection and just reply with a preconfigured username.
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