I think the reason you can't find much on it, is because it doesn't appear to be a real big issue.
I found the following at drugs.com "Hepatic side effects have included rare reports of an increase in transaminases and in alkaline phosphatase, and exceptional cases of hepatitis. No causal relationship or physiopathological mechanism between hepatitis and orlistat therapy has been established. At least one case of severe hepatic injury has also been reported. Hepatic side effects submitted post-marketing to the FDA's Adverse Event Reporting System have included jaundice, weakness, and abdominal pain. The FDA has not established an association between liver injury and orlistat at this time."
Read more: http://www.drugs.com/sfx/alli-side-effects.html#ixzz0n40lnJWT
I also got a quick glance at one article that said those most likely to get hepatitis from orlistat (the drug in alli) were those who already had the viral hepatitis.
Thanks , had a read over that just states some "rare" cases of hepatitis .
This mentions it:
http://www.telegraph.co.uk/health/dietandfitness/5749974/Slimming-pill-Alli-monitored-over-liver-fears.html