Their dedication to art vs. advertising seems doomed to failure once somebody replicates the device.
Once someone realizes that there's a company turning away customers with deep pockets, someone will show up and happily take that work. Then if they're taking the high road they have to convince artists that they have the moral high ground and therefore if a city or company wants a large mural, they'll be working with the Spraypainter team.
But the fact that they've done advertising anyway... that doesn't project the romantic image of the underdog with a moral compass that seems popular with artists. And as an artist, do you really want to use the exact same medium that every auto dealer group in town is using to advertise? Yuck. That's not a problem yet, because there's only one company doing those murals and they are only taking a few advertising projects. But once the copycats show up they'll have to find a way to differentiate their look or get sidelined.
Yeah, just like Dropbox is basically an FTP account, mounted locally with curlftpfs, and then SVN or CVS on the mounted filesystem. Not to mention that from Windows or Mac, this FTP account could be accessed through built-in software.