Yeah. Silent Spell is a feat designed pretty much to shut this tactic down. Similar with Still Spell. Or you just put a spell in a spell completion item that doesn't need a command word (Ring of Spell Storing, for example).
It's very hard to inconvenience spellcasters for more than a round or two.
edit:
The spell sticks around for the remainder of its duration, which is short enough to not worry about.If Silence is cast on a person/creature, and that person/creature is killed, does the spell end? That is, is the spell attached to the body or to some kind of philosophical essence of the being?