Depending on what mobile device you own, you'll see something that says "via device name" next to the date of your post on Facebook. If you're device is not recognized, you'll simply see a "via Mobile" note, which is what happens when I post from my phone.
If you allowed your iPhone to be called iPhone when you logged into the app, it'll show up as a recognized device on Facebook, and will post "via iPhone." Same thing goes if you have a Samsung Galaxy S3 or Nexus 7 or iPad. It could also just say "via Android." But, the default is usually just "via Mobile."
Whether it's for promotion of the brand or just to give users the ability to show off their stuff, it'll show up regardless when you post you status, unless it's not recognized. If you don't want people to see what specific device you're using, you can simply go to your Security Settings page on Facebook and delete your recognized devices.
Or, better yet, why not just screw with them? If you've got an Android device, you can change your devices name whenever you want with Status Via, created by XDA Developers member smart_desk.
Status Via allows users to choose their own "via from" when updating their Facebook status on their Android device. It doesn't matter if you don't have the device, it's still possible to post "via iPad" or "via BlackBerry" even if you're using a Galaxy S III.
The list of devices you can post from even includes things that aren't even electronic devices, such as "via Angry Birds," "via Walmart," "via the Moon," and "via Playboy Mansion."
Too bad this app only exists for Android. You can hit it up over in the Google Play Store (free).