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[edited by: tedster at 2:00 am (utc) on Nov. 14, 2006]
Not if the link target is disallowed by robots.txt. That makes it fairly obvious to GoogleBot that you didn't add the link for tricky ranking purposes.
Linked 1x1 gifs with the link target disallowed by robots.txt are one of the common methods for tracking and logging page accesses. You'll often hear them referred to as "Web beacons" in either Web or e-mails contexts.
I've been running this script (or one like it) since the latter part of 2002. The site it's been on longest hasn't dropped out of the top 3 positions in the SERPs at any time before or since.