I saw the Meet the Team Videos in some video compilation and really liked them in around 2009, and the youtube comments said the game was full of hackers so I never looked it up to see if it was worth playing because I wasn't enjoying the actual hacker-filled Combat Arms. In 2011 I was on Machinima's channel and saw that people were making a reaction video to the fact that Meet the Medic was announced so I was like "wow I'll have to watch that when it comes out".
Cut to right before they announced it was free, I was playing Minecraft and after the server went down one day I checked their forums to see what the reason was. Someone made a post that said "Play TF2 it's on free Weekend until the server gets back up
EDIT: HOLY SHIT IT'S FREE FOREVER"
So then I watched Meet the Medic and played TF2 for 2-3 months and quit until Pyromania. Only other large break was between Tough Break and Jungle Inferno.