I've been using irc since 97 and i have yet to be "hacked". Please explain how someone gets hacked, other than recieving files/trojans(that give someone else total control) from unknown people and running the file. And if you do run a file/trojan like that you obviously have the word idiot stamped on your forehead.
One way i've seen people being "hacked" is by having their file sharing option turned on for some unknown reason, this basically gives anyone out there access to your computer. Again, lets stamp the word idiot on your forehead.
If your a linux user you better have your telnet deamon turned off or someone with enough knowledge of common exploits will definetly tamper with your system, unless you patched yourself against them.
Last and not least is a dos attack, someone floods your ip with ping requests, this basically cuts your connection off for a couple of minutes or hours depending how good of a day the "hacker" is having.
How do you avoid all this on irc? Dont piss people off, or just get a shell and install bnc.
How many people on irc will "hack" you? Maybe .1 percent.
Of course this mainly happens when you piss off that .1 percent, which basically means it'll happen to you maybe once a year