Valve didn't wait long to give you a chance to play local multiplayer games online. The latest Steam beta client now includes Remote Play Together support that lets friends join in multiplayer experiences that would normally require sitting on the same couch. Only the host needs a copy of the game -- everyone else just needs a controller or (with permission) access to the keyboard or mouse. You can play across computer platforms (a Mac player could join a Windows game, for instance), and voice chat lets you yell at players as if you were there.
This is a beta, and there will likely be glitches. Valve has warned that it's focusing on improving compatibility and network stability during the test. Still, it might be worth a try if you miss face-to-face play sessions with friends. And in some cases, it might be the only way to play online. While native online multiplayer is a staple of many games, some titles insist on local play -- if you're willing to deal with a little extra lag, you won't have to miss out on that shared experience.