Xbox Preview Programs have long been popular. They're easy ways to get sneak peeks at features that won't reach the masses for weeks, if not longer. Unfortunately, though, they're now proving to be too popular -- Microsoft is warning that it's "slowing" the number of people it lets into the Xbox One Preview Program now that it's "near-capacity." The tech giant needs to "optimize" its pre-release user base for testing, according to a forum note. The timing of this move isn't all that surprising, mind you. This year represents the first time that Microsoft will overhaul the Xbox One interface, rolling in big features like backwards compatibility and the Cortana voice assistant. It's only logical that gamers would want an early look at these upgrades, especially when this portal could stick around for a good, long while.