I posted on Pioneer Basement's Forums in my work blog about Iron Bacteria as a Health Risk.
As far as the research says (currently) Iron Bacteria isn't a health risk. Having Iron Bacteria can only clog well pumps, basement waterproofing systems, or exterior drain systems that have direct access to water where the Iron Bacteria is present.
To the Basement Waterproofing Industry Iron Bacteria is more of a "pain in the rump" than anything dreadfully serious.
However, because it exists, clogs basement waterproofing systems, and helps to disrupt the dry basement that you love, I feel compelled to write about it.
This blog post on the Pioneer Basement Forums that I posted deals with Iron Bacteria's food source: Iron and Manganese.
For more formal research and understanding:
Wilkes University Center for Environmental Quality Environmental Engineering and Earth Sciences: Iron and Manganese in Drinking Water
Microbiologically Influenced Corrosion Testing
By Jeffrey R. Kearns, Brenda J. Little (p.266)