Annie H. Jeong (Wachtell, Lipton, Rosen & Katz, New York) has published Foreign Partners Deserve Their Share of the P.I.E.:  The Portfolio Interest Exemption as Applied to Partnerships, 110 Tax Notes 635 (Feb. 6, 2006), also available on the Tax Analysts web site as Doc 2006-1148, 2006 TNT 25-71.  Here is the abstract:

In this article, the author provides a brief overview of the 10% ownership limitation under the portfolio interest exemption and proposes that the limitation be applied at the partner level. The author believes that the limitation as applied at the partnership level creates unjust and unintended results, whereas, if applied at the partner level, the limitation would adequately prohibit the use of the portfolio interest exemption by persons owning 10% or more of the obligor, while allowing those who properly deserve to qualify under the portfolio interest exemption to benefit from the exemption.