Even doses as low as 1g taken daily for a week or two will show significant changes in liver chemistry. Consider that many other medicines, especially cold medicines, often include it as well, and it's not hard to see how someone that is suffering from a strong cold could end up taking more like 2-3g per day for extended periods of time. That will definitely cause some damage to the liver, which can be recovered from, but should probably be avoided. At least in the US though, many people have already compromised liver function due to chronic metabolic diseases, and for many, the damage might end up being permanent.

I've commonly been recommended 3-4 g per day by Physicians. I take 1 gram as my standard dose.

Now consider people with memory issues such as dementia where they might have a headache, take 2 pills, then 10 minutes later think 'I have a headache...'