“Required Minimum Distributions (RMDs) generally are minimum amounts that a retirement plan account owner must withdraw annually starting with the year that he or she reaches 70 ½ years of age or, if later, the year in which he or she retires. However, if the retirement plan account is an IRA or the account owner is a 5% owner of the business sponsoring the retirement plan, the RMDs must begin once the account holder is age 70 ½, regardless of whether he or she is retired.”

I’m assuming he’s not a 5% owner.

“(B) all defined contribution plans (whether or not terminated) of an employer are to be treated as one defined contribution plan.”

Note it says “an employer.” The employer is responsible for the annual addition limit. One employer is not supposed to know or track what other employers are doing to the same person. So each employer gets its own limit.

Compare that to Code section 402(g)(1)(A) for employee elective deferrals ($16,500 in 2011; $17,000 in 2012):

“Notwithstanding subsections (e)(3) and (h)(1)(B), the elective deferrals of any individual for any taxable year shall be included in such individual’s gross income to the extent the amount of such deferrals for the taxable year exceeds the applicable dollar amount.”

Note it says “any individual” which means across all employers. Any individual person knows how much he or she is contributing to which plans. The individual is responsible to stay under the elective deferral limit across all plans.