I must admit, I can't see why people have problems keeping track of conditions. People have already pointed out the newfangled concept of writing things down.
It's not just a matter of writing it down, although if you think about it, writing it down is pretty darn time consuming because it is every single round. It's a lot of bookkeeping that did not exist for the most part in earlier editions.
It's more of a matter of writing it down so that EVERY player can view it at any time. In order to make informed decisions, the players should know which monsters are debuffed, which have conditions on them, etc. They even need to know the statuses of other PCs. If the Fighter has a +2 power bonus to hit on him, it doesn't make sense to put a second +2 power bonus to hit on the Fighter.
In our PathFinder game, I am playing an Archivist/Wizard/Mystic Theurge. There are encounters where I use his Dark Knowledge. This tends to give everyone a +1 to hit most of the monsters in the encounter. If I cast Haste, I give everyone a +1 to hit for the rest of the encounter.
But, these are somewhat rare. I do not use them every single encounter. When I do use them, it is for the majority of foes and the majority of the encounter. There is very little need to track this extensively to the nth degree as to which monsters are affected and which are not. There is no need to try to determine if the effect is still up or not because it lasts for either the entire encounter, or for 6 rounds.
The issue for 4th is that the conditions, buff, and debuffs are nearly every single round for most of the combatants and it changes from round to round constantly.
It's much easier to remember and to write down that everyone is +1 to hit for the rest of the encounter than it is to keep track of a boatload of nitty little different effects that change from round to round and combatant to combatant.
The amount and difficulty of in combat bookkeeping has more than tripled from 3.5 to 4th.
And organization is not the solution. Organization makes it semi-bearable, but it doesn't resolve the core issues of too many one round effects, too many different duration effects (SOET, EOET, SOUT, EOUT, save ends), and too many single target effects.