In a blog post on Capcom-Unity, company VP Christian Svensson has addressed some "Stuff You Want to Know About SSFIV:AE for PC." Scroll down and you'll get to the catch.
"SFIV unfortunately was plagued by pirates and hackers that messed up leaderboards," Svensson writes of the original iteration on PC (which still sold well by Capcom's earlier account). "To hopefully remedy that, SSFIV:AE will be making use of what is called SSA technology."
While not as random as certain TSA measures -- SSFIV:AE players can still wear shoes and needn't limit their beverages to 3.4-ounce bottles -- the game's Software Security Assurance protocol is no less strict. Players are required to be signed into Games for Windows Live in order to access most of the game's features and content.
In offline mode, SSFIV:AE is reduced to a sort of demo, with players limited to local play only (obviously), but also restricted to 15 of the 39 fighters and unable to save settings or challenges progress. DLC is inaccessible when playing offline, as well.
Should the GWFL connection be lost mid-game, the player is given a chance to sign back in at a "logical break point" -- but should that fail ... you're in demo mode. And if you don't live in a GFWL-supported region? Svensson calls that a "buyer-beware situation."
Prospective purchasers should also be aware that Steam and Impulse will implement their respective "security solutions" (in addition to SSA), and that Steam users won't use GFWL Marketplace to purchase DLC. "We'll provide more details on that wrinkle at a later date," Svensson notes.