Most tanks are control freaks. As a matter of fact, you should hope that your tank is a control freak, because the ones who shrug off a mob running around loose are the ones you probably don't want tanking your run anyway. With that in mind, there are several player abilities that, while great for soloing or PvP, don't make the transition to a 5-man very well. Either they make life a real nuisance for your group members due to inherent design, or they tend to do so in the hands of a player who doesn't deploy them in a particularly helpful fashion.
Not all tanks will have the same degree of irritation with all of the following skills (for example, I play a druid, and because bears don't have a ranged silence, a knockback on a caster mob is much more likely to annoy me than, say, a death knight tank), but I promise you that they've all been mentioned by my tanking colleagues as abilities with a high chance of blowing a pull.