Even running a stable web or email server, where even a miniscule error can throw a spanner in the works, requires considerable administrative efforts especially during initial configuration but, imagine running sid! No real problems? You can bet your life there would be and that the system would break every so often.
It's advisable to run stable for production, i.e., for getting work done. The purpose of sid and testing is not "to get the latest software" but to track development but it's far better in a case of
Shiny_New_Stuff_Syndrome to backport the stuff to stable.
Stable is Debian's core distribution and the main reason why folks depend on is it's stability,security and reliability. But each to his own.

"Please accept my resignation. I don’t care to belong to any club that will have me as a member".—Groucho Marx