Do you have the key with you when you check if it is still flashing?
If so, try leaving the key in the house and then go out and check it.

In article
<fc9522a1-80b4-497f-a878-c716b08561a9@a23g2000hsc.googlegroups.com>,

I'll bet it's in your owner's manual...though it might take an hour to
find it. Perhaps it's listed under "useless dark current loads?"

On my 2007 Mazda3, it's the immobilizer indicator. It flashes whenever
the key is out of the ignition. I don't have keyless entry, just the
standard $150 key.

The 3's stupidest warning light is the green one that reminds me my
headlights are on. Well, duh. I'm surprised it's not accompanied by a
chime (for blind drivers, of course).

To quote page 5-48 of the owner's manual for my 2006:

Security Indicator Light

This indicator light starts flashing every 2
seconds when the ignition switch is turned
from the ON to the ACC position and the
immobilizer system is armed.

The light stops flashing when the ignition
switch is turned to the ON position with
the correct ignition key.
At this time, the immobilizer system is
disarmed and the lights illuminates for
about 3 seconds and then goes out.

If the engine doesn't start with the correct
ignition key, the security indicator
light keeps illuminating or flashing, the
system may have a malfunction. Consult
an Authorized Mazda Dealer.

thanks everyone.
dave