Maybe this isn't directly related to break-in period but since we're talking about manufacturers' recommendations, I'll throw in my 2 cents on oil change intervals. BMW has been recommending 15K oil change intervals for a number of years now. I was brought up believing that 3K oil changes were the best bet for maximizing engine life and practiced that until I bought an '03 E46 M3. Since I wasn't convinced that 15K was a safe distance to run an engine, even with synthetics, I had my factory Castrol synthetic oil tested at 7,500 miles by sending a sample to Blackstone Laboratories.
http://www.blackstone-labs.com/standard-analysis.php
I didn't track the car so my miles were probably a typical mix of commuting and occasional hard accelerations. The report I received said that, based on my usage, the additive levels in the oil were good for about 10,000 miles and then I should change the oil. Based on that, I paid for the interim changes every 7,500 miles in between the changes paid for by BMW. I repeated the test with my '08 135i and got basically the same
report back saying I shouldn't go more than about 10,000 miles based on wear rates.
Since I rarely keep my cars beyond 50,000 miles, the reduced wear on engine parts is mainly a benefit to the 2nd and 3rd owners but for those of you who keep cars through the life of the vehicle, I'd recommend paying $25 and having your oil checked about half way through the recommended oil change interval and then make up your own mind about how often to change oil.
Manufacturer marketing departments, BMW included, may well dictate the longer oil change intervals rather than sound engineering practices.