In the recent past, whenever Blizzard pruned abilities from our spellbook, it was often the most obviously redundant choices. Three different flavors of Judgment, for example, was hideously excessive. Did Seal of Light and Wisdom need to exist simultaneously? Not really, and it was easy to roll them up into Seal of Insight. Did we need to have two separate taunts? The devs felt no (I woefully would have preferred they didn't) and they cut us down to get cheap wow accounts just Reckoning.
You could go even further back if you wanted and dredge up the ghosts of all the Blessings that have disappeared over the years, if they weren't lucky enough to get repurposed into a Hand spell.
And yet even then, it can be argued that the number of Hand spells we have these days are too many. How many times do we really ever use Hand of Salvation anymore, considering how insane tank threat is? Maybe on transitions when the passing tank has a large amount of Vengeance, but never (this expansion) on a non-tank character. Could Hands be combined, like putting the Freedom effect on Sacrifice? Perhaps, and I imagine that could be buying wow accounts low-hanging fruit for a future prune come the next expansion, if the devs decide they need to cut back a bit.
There are some abilities that I hope that the devs do not usher to the chopping block, no matter how utterly inconsequential or situational they are. For example, Turn Evil: I don't think I've yet used that ability once this expansion and (confession time) I don't even have it on sell wow accounts my bars. Yet, it doesn't add to any ability bloat I may or may not be suffering and it just feels so iconic as part of the paladin toolbox (this may be my old D&D days showing) that it would be a real shame to lose. For similar reasons I was annoyed when they chopped Sense Undead, which was utterly unobjectionable outside of the silly glyph that everyone used back in Icecrown Citadel.
Closing up this topic, I'm curious what you all think. Do you have too many abilities on your bars, are you drowning in buttons? Or do you feel like there's enough room for expansion and you're not yet pressured to go out and buy a Naga?