When I order stuff from Amazon.com and send it to my ZipX account, I always say "Group my items into as few shipments as possible". That's because ZipX charge a flat rate of $22.25 for every package (plus duty and additional shipping), so getting multiple shipments gets expensive quickly.
So I when I ordered seasons 1 and 3 of "Curb Your Enthusiasm" from Amazon this week, I was careful to check they were both shipping from the same supplier. They were, and my email confirmation also stated, "order will arrive in 1 shipment".
So naturally I was overjoyed when Amazon then told me they were going to send them as two packages anyway. High fives all round.
I rushed to the website to try to cancel part of the order, but it just laughed in my face and told me they were already being prepared for shipment and it was too late to do anything now.
The really bullshit thing about the whole deal is that the shipping confirmation email for the first package said they were shipping this part of my order separately "to give you quicker service". The second shipping confirmation arrived 90 minutes later. Both packages arrived at ZipX at the same time.
I've emailed Amazon to complain, and suggest that perhaps they should warn customers before splitting orders into multiple shipments when "as few shipments as possible" has been specified. I'm not holding my breath, though.