I think TSA's approach to this is quite instructive and ultimately put my mind at ease for my upcoming trip to LHR.

http://www.tsa.gov/what_we_do/layers/secureflight/

At the security checkpoint, TSA strives to ensure your identification and boarding pass are authentic and validate you are who you say you are. Small differences in the name on the boarding pass and ID, like middle initials, should not impact your travel. It is not uncommon for the information printed on boarding passes to differ slightly from the information on IDs, depending on the boarding pass printing practices of individual airlines.


I booked my flight through Vayama, which doesn't even allow you to put more than a middle initial on your ticket. I called Vayama and they were adamant that the middle initial would not be an issue so long as first and last names matched exactly.