Reid - 4:14 pm on Jun 27, 2005 (gmt 0)
robots.txt is part of the robots exclusion standard.
It was designed to control bots use of bandwidth and keep them out of unwanted folders.
Google obeys robots.txt and there is NO penalty for having robots.txt
That being said it is possible to affect ranking with robots.txt
If you ban bots from pages you want indexed - they won't be.