[dijit]

He's not, I run an IRC network, a decent sized one.

they're prime for DDoS attacks and many attacks are hard to avoid with scrubbing.

We get attacked for anything, for, enforcing a no malicious behaviour rule, for "harbouring an enemy" of a certain group.

these kids are fickle, and IRC networks are ripe for abuse.

[cordite]

I mean, the reasoning why ISPs might block such services in use.

[spydum]

ISPs generally block them because they attract DDoS attacks like flies on... Rice. Attacks have collateral damage to other customers, and consumes a lot of support resources.