It's fine when you've read the man page at least once. If you just cowboy your way through every task, you'll never even be aware of what your tools can do. Which results in comments we've all seen: "I can't believe curl/Firefox/vim/readline/whatever can do something like that!" about something so trivial that every good poweruser/sysadmin has known it for decades (because it's in the man page).

I agree with this sentiment. But I also have personal antidotes that make me cautious about it. When I was a child I memorized dozens of phone numbers of people I called a couple times a month. Now my phone memorizes any phone number for me. We used to memorize poems and such. I can't give you any scientific reason why it is good to have memorized the Gettysburg Address. But I feel intuitively that there is some benefit to exercise your brain similar to the intuition I have about exercising muscles.

If a person thinks they benefit from 100 situps a day, I'm not going to disagree. And if they think there is some benefit in reading man pages, well, thanks to those who take the time to write all that ducumentation.

When it backfires you're screwed, I have experienced it one using curl -L