To co-opt an old activism slogan, "Silence = Death."
I was dismayed to find the old verbal spell component rules in full force. Nearly every spell has verbal components... and a simple second level spell, Silence, can effectively shut down any spellcaster in a 40 foot sphere. No save, no defense. Every cleric of 3rd level or higher should have this spell at all times in order to massacre enemy spellcasters. Of course, it also disproportionally affects PCs, since in general monsters rely on weasely "spell-like abilities" rather than casting spells.
Sure, I think binding and gagging a spellcaster should prevent them from casting spells...but a second level spell that basically functions as a minor anti-magic sphere is just too ripe for abuse.
You are grossly over-estimating the effect of a silence spell.
The casters you say it "shut down" can simply move outside the area of effect and cast spells unhindered, even if their targets are within said area of effect.
Also, that cleric throwing down silence has to make a constitution save to keep the spell from fading every time the caster you say is "shut down" or his spell-less party mates does any damage to him (such as with weapons, or by throwing things, or by walking out of the silence area and nailing the irritating cleric with some spells).
Last, but certainly not least, just choosing to cast silence means the cleric in question has forsaken all other concentration duration spells (like beacon of hope, blade barrier, or shield of faith, for some examples).
It's also a two-edged sword at close quarters. You shut down their casters, but you also shut down yours.
The Spell-Likes do present an issue in this regard. If you find it too imbalancing, you could require "verbal" activation for SLAs, particularly the more offensive uses.
Joe_the_Rat wrote:
AaronOfBarbaria wrote:
In one of the earlier playtest packets, a caster within the area of a silence spell could make a magic ability check to be able to cast spells within it. I wish they had kept that.
Saelorn wrote:
Jay_Ibero_911 wrote:
Teamwork is important:
a) Strong Athletic Fighter grapples enemy spellcaster, prevents movement.
b) Cleric casts Silence on area enemy spellcaster is in. Enemy spellcaster is shut down unless they can escape the grapple.
c) Rogue stabs enemy spellcaster, just to rub it in. 
Saelorn wrote:
lawrencehoy wrote:
Saelorn wrote:
Luke-Lightning wrote:
Saelorn wrote:
Yeah, a clever enemy spellcaster can stop my "shut down the enemy caster" teamwork trick by having an illusion of, well, a wizard, for the fighter to try to grapple. Especially if the "wizard" illusion is standing over a pit trap . . . 
Well, let's get crazy with this.
A wizard has some low level wizard cast silence a series of times. The silence spells are placed so that they fully surround a pocket where sound exists. That wizard can cast with impunity and no one would know! It would also block thunder damage. Heck, it circumvents knock's major hindrance. It's also ludicrous.
Allow players to get creative and try and have creative enemies. Or non-creative ones. These situations are, in my experience as a player and DM (25 years), edge cases. Trying to cover them all will cause tons of headaches for everyone, and attain nothing but curtailing creative thinking.
If it's a question of killing the fun, that's a different story. Talk with the player or DM and come to a concensus as a group.
EDIT: Grammar
EDIT: Fixed formatting and modified the silence-box as it was pointed out I'd misread the spell.
You can't cast silence on an object, only on a point in space.
jaelis wrote: