Picture the scene. You spent 4 hours, up until late in the night grinding PC for your void. You insult all the kids who take it seriously, and even set up your autochat to say "everyone insult x he's a noob". You get your gloves and log off.
The next morning, you log in to do the same. The log in fails. The message appears on the screen:
"Your account is not authorised to play this version of the game!" (or words to that effect)
You shit yourself. You scurry on to the runescape website, log in, and they ask you to confirm your DOB. You know that there is a fake DOB attached; you were 7 when you made the account. You enter your real DOB, and the website tells you that you have been placed in "quickchat mode" while they "confirm your information".
In short, this really fucking scared me. I thought I was banned, or that I'm going to get banned. If so, RIP main :'(