I don't see anything wrong with using leisure=pitch + sport=basketball. Whether it's used exclusively for training or for playing an informal game with modified rules to support only one basket, it's still an area that's used for playing the sport of basketball.basketball. Edit: To expand on my answer, [the wiki page for sport=basketball][1] mentions the additional tag hoops=*, which can be used to define the number of hoops. Approximately 20% of [the objects with this tag][2] have it set to hoops=1, so many mappers are mapping single-hoop areas. [1]: http://wiki.openstreetmap.org/wiki/Tag:sport%3Dbasketball [2]: https://taginfo.openstreetmap.org/keys/hoops#values

I don't see anything wrong with using leisure=pitch + sport=basketball. Whether it's used exclusively for training or for playing an informal game with modified rules to support only one basket, it's still an area that's used for playing the sport of basketball.