What's the deal with not using compact fluorescent lights (CFL) and with
'control devices'?

I see this on the packaging at Wal-Mart and online at http://www.bulbs.com/

The only thing that I can think of which would be bad to use with CFLs would
be dimmers or the photocell operated controls which make normal light bulbs
flicker as they decide to 'turn on' in the evening. I've got some photocell
controllers (screw into bulb socket) on the exterior of my house that have
multiple sensors and work some magic so that they just 'turn on' (no
flicker). I'd think that these would be OK for CFLs but there's still that
warning there.

Any thoughts or ideas on this?

Thanks,

Brad