I remember a few cases where someone was hacked because he was playing a game.
Back in the day, some people used to get hugely upset when someone with ISDN joined a QWTF server. At the time when practically everyone was using 56k and 33k or even 14k modems were not rare, dual-band ISDN, which gave 128 kbits of bandwidth was seen as a huge and unfair advantage.
Most of the time when someone was playing Quake, he could also be found with the same nick on Quakenet irc network, and by using whois command it wasn't very difficult at all to find the IP address of that player.
So people posted the IP address to some IRC channel and asked people to ping him. A couple of 56k users could very easily flood an ISDN connection with ping requests. This kind of DDOS attack was of course mostly harmless and wouldn't extend past dropping that player from the game.
But at the time, consumer firewalls were practically non-existent, which made it possible for users with more malicious intents to easily break into the players' computers through remote desktop connections and such.
Of course, all this happened about 15 years ago, and is pretty much unheard of today.
