As a frequent visitor of an Mac-related site, I came across this:
Majker Pictures is releasing a spy thriller series shot entirely on iPhone. The rest of the tools used for the series is serious, though: Avid, Final Cut Pro, Lustre, After Effects, Pro Tools (for audio). There is a team of people who worked on the production, and it looks like the team is experienced and quite professional.
If you look at their "Behind the Scenes" clips, you realise that this was a fairly elaborate shoot. Dolly tracks, fisheye lens adapter, various vehicle mounts for the iPhone, etc.. Enough money went into this production that I'm pretty sure it could have easily afforded at least a HMC-150 rental (actually, likely even an out-right purchase).
The point is, it looks like they chose to shoot on the iPhone primarily for the promotional value of it. That fact alone ("Check this out: spy thriller shot entirely on iPhone!!! WOW!!!") has brought a lot of audiences who would have otherwise never seen it on Vimeo (or YouTube). While it hasn't gone viral yet, it just started making rounds on Apple fan sites, and chances are, this will push it out to much wider public.
While iPhone is likely never going to be a choice for anyone here for serious (or any other kind of) filmmaking, it is obvious that there may be some value in exploring many unrelated possibilities that could generate promotional value for your production. Just like these guys, who shot on iPhone so that they can get maximum benefit from that fact, you could choose to shoot at some specific location, or using some specific unusual prop ("A movie with only Honda cars in it!"), or some other gimmick that may be completely irrelevant to your plot, but could bring in audiences. These guys found that in iPhone.
