Since when did instant messengers become 'competition' for IRC? As far as I can see they fulfill two different (albeit similar) roles; IM's create a quick way to talk to friends and family and other acquaintances and typically results in 'light' conversation, whereas IRC caters more for group discussion and communities, while providing for one-to-one communication also - and although the conversation on IRC differs because of the vast amount of varying channels within many different networks it is certainly well suited to 'heavier' discussion which would not work well across an IM.
Surely Microsoft's recent closure of it's chatrooms, which were by far the closest thing they had to IRC, shows that any attempt there may have been at displacing IRC has been considered a failure (by them at least) and they've decided to cut their losses by dropping the service. I'd say that the only way in which Microsoft, AOL, etc. are hurting IRC usage is not in terms of 'turning' potential regular IRC users onto IMs but by painting IRC as a dangerous nest of paedophiles and wackjobs run by irresponsible people instead of being clean fuzzy places run by *respectable* companies such as themselves which probably leads parents to prevent their younger children from using IRC. Whether I'd consider the loss of younger children from IRC a bad thing is debatable, but just the same it could be responsible for the so-called plateau in user-gain that the original survey Clockwerx posted spoke of.
