SONEs are not simply SNSD fans.
SONEs are at one with the SNSD members.
A SNSD fan might purchase the music of other groups such as Wonder Girls or KARA, or they might leave positive YouTube comments for these groups.
SONEs, however, will not do this because they understand that these groups actively compete against SNSD.
A SNSD fan might think it's best to just ignore SNSD antis (anti-fans) and false rumors about SNSD, whereas SONEs actually work to take down antis and to dispel false rumors.
SNSD fans often take everything the SNSD members say as fact, but SONEs know the SNSD members so well that they are able to tell the difference between fact and a PR statement.
SNSD fans usually purchase SNSD merchandise with the merchandise in mind, whereas SONEs purchase the merchandise with supporting the SNSD members in mind.
SONEs would actually rather send their money directly to the SNSD members, without receiving any merchandise in return, because this would provide greater support.
SONE is also the name of the official SNSD fan club.
Of course I did, I'm a SONE.