Yahoo, and sleep at 6 months

Thank you for all your birthday wishes!

I'm snowed in today and snowed under a pile of schoolwork.

Read this from my friend Carolyn Edgar about the Marissa Mayer Yahoo no-telecommuting thing:

Now, question:

Is there a sleep regression at 6 months? It seems like some kids START sleeping at 6 months, but others STOP sleeping at 6 months. Is this some kind of developmental thing and different kids just have opposite sleep reactions to whatever that developmental thing is?

Hand me some data points about whether your kid slept better or worse at 6 months than at 5, and anything you think accounted for that.