It's part of the reason I think people needed to adjust their viewpoint when they complain about certain quests making them feel evil. Unless your character is completely insane, it's highly unlikely he's going to do EVERY SINGLE QUEST for every single faction. Skyrim seems designed for multiple playthroughs if you actually enjoy any form of roleplaying versus simple gameplay (which isn't wrong).
This is very true, and actually is quintessentially TES. Some of us won't ever do the "evil" stuff - but it's not a bad thing that it's there for those who have no issues RPing it.
the thieve's guild in this game is more like the mafia...
No, it's not. *sigh* The mob is a worldwide organization of serious criminals, with fingers everywhere from the oriental laundry in Honolulu to the Winter Palace's kitchen in St Petersburg. The TG in Skyrim is a loose conglomeration of every slimy two-bit creep who thinks he's pegged "evil" simply because he reads porm by candlelight in the sewers of Riften.