I've posted a few times regarding how I enjoy finding ways to automate little tasks. However, this can have a downside. David Sparks recently relayed an example of this on his MacSparky blog.
I have a similar story. A long while back I decided to divert all the email from my EyeDock website into my Gmail account. I liked the idea of only opening one email account, and I liked Gmail's tools much better than the web panel my hosting site gave me for managing email. I simply grab the email via POP3 and filter it to skip the inbox and apply an "EyeDock" label.
However, I initially got a little label crazy and created about 6 different EyeDock labels (EyeDock, EyeDock:subscriptions, EyeDock:companies, etc.). I decided I was making making my life more complicated than it had to be. After all, when I want to find an email I rarely use the labels anyway because Gmail is just so searchable. So, I eliminated some of my extraneous labels and simplified my life.
As the next month went by something seemed a little off, but I couldn't figure out what. And it seemed different in a good way: I had more time in my evenings to work on the things I wanted to. However, I eventually received a couple messages from people stating that I hadn't responded to their emails (which is odd because I've prided myself on making great efforts to reply to my EyeDock users). When I searched Gmail for their previous emails I found them, but they were not in my inbox and they didn't have any labels.
I realized that I'd made a mistake. I originally was filtering all emails that were originally directed a specific EyeDock address into a specific Gmail label. It was working well ... until I deleted that label. I guess I assumed that, if the label didn't exist, the emails would show up in a parent folder or at least in the inbox. Nope. Instead they were just sent to the magical land of "archive".
So, I searched for all the messages that were sent to that email address and found about 60 of them. These were questions and concerns that were directed to my business and I'd never replied = really horrible customer service.
I went through the missed emails, one by one, tried to address their concerns, and profusely apologized (I made a TextExpander snippet to help with that).
I learned my lesson: Automation is great, but you really need to be careful. It always does what it's told, but you need to make sure it's doing what you intended. If not, you might negate all the time you saved - and then some.