[unfasten]

> And on most carrier locked Android phones, you have to find an exploit to root your device before they let you sideload apps.

This is wrong.

Allowing this is built in to Android and it's a user togglable setting.

Verizon explicitly mentions sideloading and how to enable it:

http://mobile.vzw.com/LocationAgent

    For Android devices, please confirm the device's Location Services
    setting GPS and Verizon Location Services (if present) are set to
    on and the device's Settings > Security > Unknown sources is checked.

http://cache.vzw.com/multimedia/mim/mot_droid_razr_hd/razrHD... PDF Page 15:

    To let your smartphone install apps that are not from 
    Google Play, tap Apps  >Settings >Security & Screen Lock
     and check Unknown sources

Ditto AT&T:

https://www.wireless.att.com/businesscenter/en_US/pdf/att-to... PDF Page 3:

    In order to install these apps, you must ensure the 'Unknown Sources'
    box is checked [...] Follow the instructions on your phone to enable
    this feature and continue with AT&T Toggle installation.

http://www.att.com/esupport/article.jsp?sid=KB410684&cv=820

    Before you begin, you'll need to set your Android smartphone
    to allow downloads from non-Market sources by selecting Unknown sources
    in the Settings menu on your device.

Ditto Sprint:

http://eguides.sprint.com/support/eguides/htcone/content/htc...

    Go to Settings > Security, and then select the Unknown sources
    option to allow the download and installation of the tool
    through your Web browser.

http://eguides.sprint.com/support/eguides/sprintvital/conten...

    If you want to install apps from sources other than the Google
    Play Store app, you must allow the installation of apps from
    unknown sources first.

[drcube]

Fair enough. I've seen phones that disable the setting for allowing sideloaded apps. But fortunately it's not as prevalent as I thought.

[victorhooi]

Can you name any handset that do that?

I've honestly never seen it before, and I'm curious what manufacturer would actually do this nowadays.