See also WebMD.com's article about Mastitis.
Frequently Asked Questions
About Inducing Lactation
Are there health risks from breastfeeding?
The biggest risks are side effects from excessive use of Domperidone and Mastitis (warning:NSFW). The chances of having the latter can be lessened with Lecithin and proper latch techniques. The Piercings and Lactation page (warning:NSFW) addresses this concern as well.