I find that the reverse is usually just as bad (or worse). When a player/DM refuses to wing anything, needs to keep track of every second of every day in campaign, requires alignment/motivational justification for the act of picking one's nose, etc., the game begins to take on a rather laborious quality. I have a DM/player who is so obsessed with keeping track of every detail and ensuring absolute "realism" (*ummm... magic?!?*) that I often feel more like I'm working than playing a game. Her strict adherence to things like average character wealth and the unwillingness to improvise to provide characters with the opportunity to pursue prestige classes without training for five levels beforehand... when the prestige class wasn't published until yesterday... it makes the game suck. For the sake of realism, the party has a chance of encountering a hostile Great Wyrm Red Dragon during a random night encounter at 15th level... It breathes. We die. There goes a year of gaming... break out 4d6!! A DM/player needs to be able to rewrite the letter of the law a little bit to enhance the gaming experience of everyone involved.
As far as weighting things in favor of the NPCs, I don't have a problem with starting a challenging adventure with a little extra firepower, but when the power level of an NPC party member makes the PCs seem superfluous on a consistent basis thoughout a campaign, there's definitely a problem.
At the other end of the spectrum, I have (had) a DM who consistently responds to good play and planning by breaking out the +10 vorpal Nerf bat. "What? You cast a spell that I expressly approved which kills my BBEG in one round? First of all, it backfires and affects you instead because of divine intervention. Oh, yeah--it also drains all spellcasting ability from your character. You are now a 20th-level wizard with no spells. Permanently." Ugh... Yeah, we all basically shunted that guy off to another dimension. The sad part is that he used to run some of the best games I've ever played in my life. The guy can play 30 different NPCs in a session and you can tell them all apart each and every time you encounter them, describe a scene off the cuff so vividly that you can smell it... What a shame.
Don't get me started on cheating players...