Come into my parlor, said the spider to the fly.

A warning to the naïve, this phrase has twice been directed at me. 

It references a poem by Mary Howitt published in 1829 about a naïve fly ensnared by a less than honest spider.

I have met some spiders in my time; but, I really never thought myself to be the fly.

Why, then, have I bumped up against these words more than once?