Ok, I've gotten to the bottom of the mysterious creeping 100% load problem.

The problem is NOT Squeak's, and has nothing to do with Speaker. :)

As a Linux fan, I've been beta-testing the soon-to-be-released KDE 2.0
desktop, which comes with a sound daemon called aRts (which I've mentioned
here).  It has a program called 'artsdsp' which you can use to make any
non-aRts capable programs use the sound daemon by intercepting OSS sound
driver calls (it's kinda neat, it actually works quite well for certain
apps).  I've been using it with Squeak for several weeks now and it
works great.

However, there is a side-effect, in that it will eventually drive Squeak's
load up to 100%.  I have no idea why, but oh well...the problem isn't
Squeak's, in the end.  The 'proper' way to use aRts is to aRts-enable
the sqUnixSound.c module, something I may attempt sometime.

So anyway, mystery solved.  And this serves as a heads-up to any 'NIX
users that might be using KDE 2.0 (or more specifically, aRts) in the
future!  Use artsdsp with care...it might have side-effects.

(For anyone interested, artsdsp isn't actually a program...it is a shell
script that uses the LD_PRELOAD environment variable to forcibly load
the libartsdsp.so compatibility library first, which somehow is able to
intercept OSS sound calls.)