We have a similar problem as the people that had the "odd stain" in the linolium around the toilet base of the toilet only our floor is concrete and the stain has creeped further away from the toilet base.
It looks just like the picture sent by Dave7F15 on Oct. 17, 2007 only ours is worse.
Do you think this is a seal problem as well and will it affect the concrete?
Thank You
Kim

Kim, we can't see Dave's picture because we have no link. Can you cut and paste or give the link? Any staining creeping out from a toilet base makes me think the wax ring has failed.