My 16 month old hasn't started asking "why". I'm actually looking forward to that stage a bit. :) My mom is looking forward to it. Evidently I asked "why?" for about 3 years straight. and she wants to see what I do as the parent. I've been looking at buying a copy of an encyclopedias in preparation.
I've used .mac and most of the other services you mention for quite a while. Where .mac really shines is when you have multiple computers running OS X. My assistant and I share the same address book (which we could do with Plaxo), but I can also take a peak at her screen from my computer anywhere in the world using Back to my Mac. In the same way I can connect to her hard drive and vice versa.
For me the .mac account is well worth the small expense--even if I could get similar functionality for free using a bunch of other components. The easy of use is hard to beat and having a reliable system is worth quite a bit.
I tend to agree, but there are still a lot of people who use them. I live in a small enough town now, that the phone book is only about 1/4 inch thick and I've actually used it to find people that weren't available on a Google search.
