Just as a point of interest along a similar vein, in 2009 I was returning to BNE from MIA on two separate PNRs....MIA - LAX (AA) and LAX - BNE (QF) both the cheapest of cheap fares I could find which were booked separately on the internet. I think I had an allowance of 2 pieces on QF and none on AA. At curbside check-in at MIA, I presented my MIA - LAX itinery and the guy asked if I was going further so I then showed my LAX - BNE itinery. He said "no problems, I'll just check your luggage right through to BNE and save you the AA luggage fees" (approx US$100 IIRC). I shared the windfall with him by tipping him $50 for his efforts (I also had no idea what was expected as a tip for curbside check-in). When I posted that story previously on AFF, someone advised that curbside check-in are not supposed to through check int luggage. Does anyone know what are the actual rules (laws?) regarding that, as I'd be keen to take advantage of that again some day?