Wikipedia actually has a decent description of the negotiation that led to the supposed "typo." It was no typo at all; it was intended compromise.
Patient Protection and Affordable Care Act - Senate:
The Senate began work on its own proposals while the House was still working on the Affordable Health Care for America Act. Instead, the Senate took up H.R. 3590, a bill regarding housing tax breaks for service members. As the United States Constitution requires all revenue-related bills to originate in the House, the Senate took up this bill since it was first passed by the House as a revenue-related modification to the Internal Revenue Code. The bill was then used as the Senate's vehicle for their healthcare reform proposal, completely revising the content of the bill. The bill as amended would ultimately incorporate elements of proposals that were reported favorably by the Senate Health and Finance committees. With the Republican minority in the Senate vowing to filibuster any bill they did not support, requiring a cloture vote to end debate, 60 votes would be necessary to get passage in the Senate. At the start of the 111th Congress, Democrats had only 58 votes; the Senate seat in Minnesota ultimately won by Al Franken was still undergoing a recount, and Arlen Specter was still a Republican.To reach 60 votes, negotiations were undertaken to satisfy the demands of moderate Democrats, and to try to bring several Republican senators aboard; particular attention was given to Bob Bennett, Mike Enzi, Chuck Grassley, and Olympia Snowe. Negotiations continued even after July 7 when Franken was sworn into office, and by which time Specter had switched parties due to disagreements over the substance of the bill, which was still being drafted in committee, and because moderate Democrats hoped to win bipartisan support. Then, on August 25, before the bill could come up for a vote, Ted Kennedya longtime healthcare reform advocatedied, depriving Democrats of their 60th vote. Before Kennedy's seat was filled, attention was drawn to Snowe because of her vote in favor of the draft bill in the Finance Committee on October 15, but she explicitly stated that this did not mean she would support the final bill. Paul Kirk was appointed as Senator Kennedy's temporary replacement on September 24.
After the Finance Committee vote, negotiations turned to the demands of moderate Democrats, whose votes would be necessary to break the anticipated Republican filibuster. Majority leader Harry Reid focused on satisfying the Democratic caucus's centrist members until the holdouts came down to Joe Lieberman of Connecticut, an independent who caucused with Democrats, and Ben Nelson, a conservative Democrat, representing Nebraska. Lieberman, despite intense negotiations with Reid in search of a compromise, refused to support a public option, agreeing to vote for the bill only if the provision were not included, although it had majority support in Congress. His demand was met. There was debate among the bill's supporters over the importance of the public option, although the vast majority of supporters concluded it was a minor part of the reform overall, and Congressional Democrats' fight for it won various concessions, including conditional waivers allowing states to set up state-based public options such as Vermont's Green Mountain Care.
It's clear that the removal of federal exchanges (the "public option") was the result of compromises made to get the bill passed. Now, Democrats want the Court to say that they always intended for all states to get federal subsidies.
-PJ
“If you’re a state and you don’t set up your exchange that means your citizens don’t get tax credits.” - J. Gruber
https://www.youtube.com/watch?v=GtnEmPXEpr0&feature=youtu.be&t=31m25s
An excellent resource: