Its depends on what folks mean by "throw media".
Even with the x90 players, you were able to throw media from apps on your phone to the player. It worked in several ways:
1) Via a DLNA remote app. Browse your DLNA server (on your phone/tablet) and "throw" it to the player. This worked for both video, audio and photos. Apps tested: Audio Remote (sony) - supports audio only, imedashare - supports audio, video and photos , tv sideview (sony) - supports audio, video, and photos.
2) Via the Sony Mediaremote app. You could browse select Sony Entertainment Network service provides, e.g crackle via the remote app and then "throw" them to the player.
3) Via the Sony Mediaremote app, you could browse the web and throw the page to the player
The x100 players do similar ... but I haven't found a way to do option 2) currently. You're also suppose to be able to search for something via TV Sideview and then throw it to your player ... stuff like netflix, youtube, local media ... but right now its very buggy.
Just to clarify "TV Sideview" works with both x90 and x100 players, its just the functionality is a bit different depending on the player family.
Above this, the new players (at least the 5100) may have NFC capability too ... but not sure how that works, or whats possible.
BTW, the price at J&R for the 3100 is $1 off, not $10.