Romney's Returns Rumors

There are so many reasons for Romney not to release his federal income tax returns.  Choose your speculation from the following:

1. He participated in the 2009 IRS Swiss tax haven amnesty.
2. He paid zero or negative taxes in one or more years.
3. He voted illegally in 2010.
4. He lied on legally binding documents about his status at Bain between 1999 and 2002.
5. He has various issues related to tithing (not 10% or more than his taxes).
6. He built his $100 million IRA using dubious means. (This may not be detailed in the returns, though.)
7. He gave $100 million to his sons using dubious means
8. He's worth a heck of a lot more than $250 million.
9. He made lots of now-embarrassing donations earlier in his career.
10. He committed outright fraud. (This is the least likely, IMHO, as his companies have shown considerable skill at legally "evading" taxes.)
11. He’s Mitt Fucking Romney, and he’s told all you people need to know.
12. All of the above

Presidential Candidate Tax Returns

From what I can tell, below are the years for which various presidential candidates and presidents have released their tax returns. Bold checks are for returns released as candidates, "e" is for estimate, "s" is for summary, and "p" is for partial.  Click to embiggen.