I comment on this article with some degree of trepidation...i'm older and wiser now (hopefully) but I can very safely say that this statement is just factually incorrect. Back in the day, late 70's and early '80's, a gram (1000 milligrams) would be an evening's entertainment for 2 maybe 3 people (in addition to the weed and booze that was also consumed). Thankfully it was never my cup of tea (like i needed artificial stimulants - oh wait, I was a coffee addict), but I certainly knew my fair share of users whilst in college. 20 or 30 milligrams over the course of the day would have about the same effect as a jumbo coffee at 7-11.
Maybe back in the old days the product was a little less diluted?