Don't tell me how fast I read
I'm not sure who originated the practice, but when I see "5 min read" or "10 min read" on Medium and elsewhere, my first reaction is how do you know?
While I think Medium's huge photo headers and "Next in" footer-based navigation greatly enhance the presentation of long form essays online, I think estimated reading times are a feature that need to go the way of social sharing buttons, blog rolls, and tag clouds.
Estimated reading times are irrelevant
Reading estimates appear to be a more approachable way to indicate article length based on word count and the reading speed of the average reader. After all, "5 min read" seems clearer than "1,350 words", doesn't it? I've written a fair amount and word counts still mean nothing to me.
But neither do estimated reading times. My decision to read a piece has never once been informed by how long the site suggests it would take me to read it. If it looks interesting, I'll start reading. If I run out of time, I'll save it for later. The web already has built-in indicator of content size -- the scrollbar.
Estimated reading times assume linear reading
Since reading estimates simply divide the total words by the speed of an average reader, there's an implied assumption that I'm going to read the entire piece and not follow hyperlinks to other content. I would hate to see actual reading times for Wikipedia articles.
Estimated reading times are insulting
There's an even bigger, more personal reason I don't like reading estimates. I don't read as fast as I would like. I blame farsightedness, astigmatism, a wandering mind, and a strong desire to read for comprehension. Sure, how I feel about my own reading ability is my problem, but I'd bet I'm not the only one who feels this way.
Every time I see "5 min read" I read it as "5 min read - you'll probably need 7 or 8." ಠ_ಠ