Especially if you have had a bunch of individual interviewers, who are all conducting multiple interviews per week and trying to ship product, the delay may be down to waiting for one or more of them to submit their feedback about you. I've definitely been terrible about that when we had some product fires going on, and got in the habit of trying to write up immediately after the interview, but sometimes with back-to-back meetings all day it fell off the stack. Knowing someone out there is waiting to hear back is a horrible thing though, and usually spurred me to try and be super-fast -- but you only need one overworked, or sick, interviewer to fall behind with feedback and you might be waiting weeks for the full interview report to be ready for hiring review.