To each their own, but I did find more than few reviews from people that had their phone fall out either due to the arms losing grip over a pothole or something, the phone sliding downwards without them noticing and eventually falling out, or nearly falling out.
Yes, I now probably 90% of these situations is a result of people not using the secondary rubber "net" thing, but that seems like a bandaid to an otherwise iffy design, and if I'm not mistaken....this was not originally part of the mount, only being added after a rash of phones falling out. Yes, the case I linked to has one as well, but it's more or less a secondary emergency backup thing, not essential, without which the phone can fall out - I like the fact the case I linked "locks" on the corners of the phone.
Most concerning to me was that apparently the little rubber legs occasionally fall off, not only letting the phone fall out, but making the mount unusable afterwards unless you can find the leg. Apparently it flops around a lot as well.
I did a lot of reading on it a few months back when I was bored one long winter day and was thinking motorcycles. Most of what I'm basing my opinions on were threads I found at advider,
including this one, as well as reviews at revzilla from riders who also had their phones fall out.
It didn't strike me as a mount I was willing to buy as a result, especially for the price.
