We have decided to remove the prize limit for Act 1 and give away an unlimited number of t-shirts. What this means is now everyone who completes any Act wins a prize! The 25% rule for Acts 2, 3, and 4 will remain in place, but if your name is not selected from one of those drawings, you'll still get one of those awesome Diablo/Gaming.SE t-shirts that Jin designed.
The Rules on diablo3acts.com will be updated shortly to reflect this change. In the meantime, keep doing what you're doing!
[Edit]: These t-shirts are in such high demand that we've decided to give them to everyone who completes any Act! What this means is no matter which Acts you complete, you'll get a t-shirt. If you complete Acts 2, 3, or 4, you'll be entered into the raffle for another prize, and you'll get a shirt regardless of whether you're selected.