When is a fan a fan?

[s_forbes]

Things like this have been allowed in the past, as long as the inspectors deem it safe. 2009 was a fun year for fans (heh), since the limited traction from wheels made thrust provided by fans actually significant. Examples: team 45,
team 1771

Also, some cool fan based manipulators were used in 2010, where you weren't allowed very much contact area on the game piece (soccer balls). Team 25, team 706