I guess I am being a baby, but numerous people told me not to go above a 600 for my first bike. They said 500 was a pretty good compromise for beginner and shouldn't get bored of it too quickly. I have no experience other than the two days I rode a motorcycle in the class you take to get the DMV riding test waived.
She sums my opinions up pretty quick, I however believe a 650 cap (twin motor) is about the end of the spectrum for beginner bikes.
I like how Mr. Regular puts the "start small" argument.
If your brain has anything resembling a frontal lobe, you'll be fine on a big bike.
250s and 500s are so cheap though.
I started at the higher end of the spectrum on a ninja 650. I was fine on that one, kept it pretty civilized 95% of the time. The other 5% was delinquency of some sort.
That being said, I now have the 675 that Mr regular refers to. If that was my first bike, I have no doubts that I wouldve wrecked a lot sooner than I did. I have to slightly disagree on the comments that theyd be fine on a bigger bike.
You don't just have a faster bike. You have a reduced throttle twist (often a 3/4 turn throttle to be at max), normally 4 piston brakes (which is good until you grab a handful and then stoppie), etc...
As one of my MSF put it "When you make a mistake on a beginner bike, it's going to turn around, bare teeth and snarl at you, all the while reminding you that's not a good idea. A race replica will bite you and be hundreds of feet down the road, while you're lying in a ditch on the side of the road."
Bit if an exaggeration, but that always stuck with me.