In practical Haskell people rarely use mappend eschewing it for the more generic (<>) operator. Personally I think it's exactly for the reason stated above—mono

In practical Haskell people rarely use mappend eschewing it for the more generic (<>) operator. Personally I think it's exactly for the reason stated above—monoid is far more general than "appending". In particular, it's easy to define a reverse monoid for any (non-commutative) monoid such that append becomes prepend. It's easy to construct monoids which have different spacial properties like Diagrams' "stacking" monoid (they have many others, too, see this entire paper http://www.cis.upenn.edu/~byorgey/pub/monoid-pearl.pdf http://www.cis.upenn.edu/~byorgey/pub/monoid-pearl.pdf). It's also easy to construct monoids which don't have any spatial sense at all like set union.