Back when 1.10 was still in the testing stages, There was a discusion thread regarding planar mapping, and how it doesn't work properly.
The end result was a concensus that the Lindens need to add a "True Mapping" or "Face Mapping" map type to the texture controls.
Can this PLEASE be implimented in 1.11/12?
Relevant threads:
/290/03/105624/1.html
/290/f2/105710/1.html
/290/15/107089/1.html
/139/f0/109525/1.html