Guesstimate this

I hereby and forthwith add the use of the word "guesstimate" to my growing list of style/grammar/word choice errors that should not be tolerated.

We already have estimate, meaning "to calculate approximately" (v.) or "a tentative evaluation or rough calculation" (n.). We also have guess, meaning "to predict (a result or an event) without sufficient information" (v.) or "a conjecture arrived at by guessing" (n.). It's one or the other, people. You're either making an educated estimate, or you're making an uneducated guess.

Yours truly,
The Department of Linguistic Purity and Common Sense