Is your concern primarily content database size?

Maybe it was some weird dream... but
somewhere I saw something on scaling  My Sites and some special considerations
that needed to be made. Now ...where that was... I'm still scouring the internet
for.

I haven't seen that, maybe in a PowerPoint deck from Microsoft at a conference?

Scaling My Sites is basically like scaling  any site collections. Just set up 40
or so content databases for your worst-case scenario and have the
warning/maximum limits match. They should round-robin quite nicely. The more
databases you add, the more SQL connects, so maybe you could start with fewer
and just keep a close eye on the sizes?

So, if your maximum DB size was going to be 200GB (let's say for fun, I don't
know what's good  for you) then maybe you cap databases once they are at 100GB to
provide room for growth? You can move My Sites around after the fact, but I
doubt that's what you want to do in your spare time

It could have been. I've been to a handful of conferences/EBCs... etc. Just
wanted to make sure they are going to scale really. This is our first HUGE
attempt at user adoption of My Sites... although they were there/hardly used in
2007... we're really hoping that 2010 will generate some excitement.

I have not been to any classes in Seattle (other than a few trips to the Redmond
campus).