Yeah there's plenty of completely clueless drivers on the road. I had nearly the same thing happen to me, ie being in a right hand lane and then some clever dick going 30-40 km/h slower than me decides it'd be a good idea to merge just as I'm about to hit him. Needless to say I slammed on the brakes and swerved as close to the barrier in the middle of the road as I could, just managed to slot in behind.
Anyway, later on, we were 'merging' from two lanes to one and he cuts me off again!! Then he beeps, puts his hand out the window and tells me to pull over to the side. I comply because I want to know how retarded this guy is. He starts lectureing me about how he could've been killed and if his kid was in the passenger seat then he could've died. Then he goes on to say "I was in the military and I was a military driver you're just some young idiot and I just want you to not let this happen to someone else".
At this stage my brother (passenger) was about cracking up laughing as he's got a national rally license plus I'm toying with the idea of getting one myself - yet this ass-wipe was trying to pull some kind of age/experience rank on me! Of course, didn't take long before I told the guy he was an irrational tool and I just drove off.
Such is the state of drivers on the road I guess it's only a matter of time before a real out-of-control P plater hoon actually doesn't avoid this guy's retarded lane changing and cleans him up.