Interested party comment. Firstly Justin is not correct when he says he was standardising members of Category:Lists of songs by authors or performers, there are  
List of cover versions of XXXX, 
List of songs written by XXXX, 
List of songs with lyrics by XXXX (Justin actually moved one to this this week!), 
List of cover versions of XXXX, 
List of singles by XXXX
List of unreleased XXXX songs, 
List of xxxx songs, 
List of songs by XXXX. 
List of songs recorded bv XXXX, 
amongst others. 
Taken with "songs written by, then the written/recorded by would have been the majority! If Justin had started amongst those single individualistic titles he would have had my blessing!
All the Leona Lewis move does, and several others (but not necessarily all) is to ignore the content and subject matter of the article and to move according to where one person thinks WP wants it. I have placed a requested move on the Leona Lewis list and several others and opposed Justin's requests for moves where appropriate. I have also moved a couple of lists that state "List of songs recorded by" to where they belong. 
For what it's worth, I have always preferred 'Songs recorded by' as it is specific, easily understandable and eliminates entries for one live performance on a wet Wednesday in Wichita (ie non-notable). List of Richhoncho songs could mean what's on my ipod today!