Affect vs. Effect

Recently I sent out a survey related to a study I began at work, looking at blogging and microblogging behaviours. The study actually started as a secondary topic, the primary being a design/display project for the summer, to display IBM-related tweets. The goal of the study was to find out how microblogging and blogging practices interact, if at all. When I was going over the open-ended answers in the survey, I noticed that I had written this sentence:

If you both blog and microblog, how has your use of either tool affected the other?

At first, I groaned inwardly--what utter mortification! Did 300 people just see a huge grammar error? Is it not an "effect" that I'm asking about, and not an "affect"? Should it not be, "[...] how has your use of either effected the other?" But comparing "effected" and "affected", the former doesn't look right either.

Now completely confused, it's time to turn to Google to do the work for me. A suggestion is given for "define: effected"--"Did you mean: define: affected?" Accepting the new search yields this as one of the answers:

affect - have an effect upon

Ah-ha! Hello, confusing near-homophone! And now I remember a simple rule, which is often broken:

affect = verb ("My blog will affect my microblogging habits.")
effect = noun ("My blog has an effect on my microblogging habits.")

So it seems that my original sentence was correct, and there was no need to second-guess myself. Yet despite the simplicity of separation, the two words are easily confused.

For a longer (and probably better) explanation, check out Grammar Girl's article on this very topic. More confusion can be supplied by Randall Munroe.