Yes and very strange behavior
I have played with the site and I am probably included in the 8 million, even though I have not been on the site for over a year and can't even remember the particulars.
The idea of getting that engrossed in the limited virtuallity of a computer screen is a bit sick imo. If it were true virtual reality in the ultimate sense, it would be easier to understand the addictive nature.
Of course each individual has their own idea of how engrossed they are but anytime you spend a ridiculous amout of time on one thing it is probably unhealthy