Using TOR? get lost!

[vukki starborn <vukki.starborn@xxxxxxxxx>]

Not long ago i've got interesting reply from one of the IRC servers:

--- You (*@207.44.180.3) are banned from this server: Tor proxy detected.
--- Closing Link: ********[id@xxxxxxxxxxxx] (K-lined: Tor proxy detected.)

So, it means that server denies connection because the client is using
tor.
Questions:

1. Did anyone from community experienced such, eh, "discrimination"?
2. How they realised that connection torified? blacklisted ip?
modified tor client that keep track of running nodes? or something
else?
3. Though the people running server is in their rights to refuse any
connection (as mentioned in their disclaimer), to what consequences
may lead widespreading of such policies? If owners of the popular
services will refuse torified users, how one can get anonymity?