Whoa what do we have here, it appears that the new Samsung Infuse 4G now allows for side-loading apps. Something no Android phone on AT&T has been able to do before. From our hands on with the new Infuse 4G it looks like you are now able to select the box "Unknown Sources" and can now install non-market applications. This is huge news because until now users have had to resort to tricks and hackery to side-load applications to AT&T phones.
See the photo above for the hard proof. That is the new Samsung Infuse 4G on AT&T, and it is allowing non-market installs. For now as far as we understand AT&T policy is still the same, and they do not allow the installation of 3rd party applications. So either this is brand new, just breaking. Or Samsung forgot to lock it down on the new Infuse 4G.
We don't have a lot to go by yet for this, we are looking into it now and will report back as soon as we hear more. For more information on the Infuse 4G go here.