Ask HN: Which NAICS code do you use to classify your SaaS?

Hey SaaS owners out there, which NAICS code do you use to classify your SaaS? I've always struggled to select a proper code in the North American Industry Classification System for a standard SaaS web app.

Classification starting point:

http://www23.statcan.gc.ca/imdb/p3VD.pl?Function=getVD&TVD=118464

Codes I've found to be somewhat in the right ballpark:

518210 - Data processing, hosting, and related services:

http://www23.statcan.gc.ca/imdb/p3VD.pl?Function=getVD&TVD=118464&CVD=118471&CPV=518210&CST=01012012&CLV=5&MLV=5

541514 - Computer systems design and related services (except video game design and development):

http://www23.statcan.gc.ca/imdb/p3VD.pl?Function=getVD&TVD=118464&CVD=118471&CPV=541514&CST=01012012&CLV=5&MLV=5

541990 - All other professional, scientific and technical services:

http://www23.statcan.gc.ca/imdb/p3VD.pl?Function=getVD&TVD=118464&CVD=118468&CPV=54199&CST=01012012&CLV=4&MLV=5