Richard Winchester (Thomas Jefferson) has posted Equity Undermined: The 1918 Check-the-Box Entity Classification Election on SSRN.  Here is the abstract:

Ever since 1996, the government has allowed virtually any unincorporated business entity to choose whether it should be treated as a corporation for tax purposes. Widely referred to as the check-the-box entity classification regulations, these rules represent a dramatic break from the approach taken under the regulations they replaced. However, the idea of allowing a business virtually unrestricted freedom to choose its tax classification dates back to the Revenue Act of 1918, just five years after Congress enacted the permanent income tax.

This brief article recounts the story behind that first, relatively obscure, elective entity classification provision. It also explains how that provision and its modern day cousin may undermine certain basic notions of equity that any sound tax system should seek to advance.