Yeah, you can have confidence in your own skills and know what you're doing, but then when you throw in four other people on your team, the possibility for errors jumps up higher and higher.
For example - keep in mind, I've been gone for a year so the lot of you probably don't know or have forgotten that I essentially only play botfights to kill time when no one else is on WoW for me to play with - I was just in a game where mid Morgana dc'ed about three minutes in and Talon kept afk-dc'ing. It was me as AD TF (loads of fun, by the way) Junglewick, and Zyra.
Warwick, Zyra, Twisted Fate, Morgana, and Talon would've ended up being a curbstomp game against bots anyways, but it essentially stayed a 3v5 the entire time. It took some excellent ganks on Warwicks part to keep the bots down while Zyra and I split pushed straight up through the Nexus. We kept our early-game advantage from not having to share CS with lanemates and managed to crank out a win in about 20 minutes or so. If it'd dragged on, Galio, Fiddle, and Annie would've melted us while Sivir stood in the back and shouted at them. I don't remember who the last bot was, it never really came after me and was pretty much dead all the time.
Point being, went into that game with Morgana and Talon arguing over who got mid (Talon, mid? yeahokay) and they both ended up being absent for pretty much the entire game.
That's what you risk when you PuG your teammates, and that's just something you have to be willing to risk.
