Seeing that the designer/developer of Skeleton (@dhg on twitter) is a designer at Twitter now, I'm sure there will be plenty of mash-ups between Bootstrap and Skeleton.

At least, it gives me something to hack on this weekend :D

They are different. In months past I have been mashing up components of bootstrap with skeleton (as well as 2 excellent others, golden grid system and frameless by @jonikorpi) in order to have sensible css defaults that work responsively. GGS made some things possible without modification that were very tough to implement in skeleton (like the footer at the bottom of goldengridsystem.com)

I use Skeleton on my blog.

You're worried that it's missing some features? Skeleton has no features. It's a grid, some typography, and some defaults. On the other hand, Bootstrap is a complete front-end package. They're very different. Look at Bootstrap's js bundle alone.

Skeleton is nice when you just want some sensible defaults with your responsive grid.