I found the complete opposite of what dlondon says to be true.
I live in an apartment block and have a caretaker/receptionist who manages deliveries and stuff. When my iPhone 4s was delivered, I just happened to be downstairs at the time and the UPS guy couldn't give me my phone until I went back upstairs to get some ID. He said he wouldn't have been able to leave it signed by my caretaker because they were under quite strict instructions from Apple not to leave it with anyone other than the buyer/household. As such, I don't believe they are allowed to leave it with neighbours because of the value.
I think a lot of it is down to fraud as well, because it stops people from stealing identities and card details to buy goods and get them delivered elsewhere.
I can actually speak from experience on this one. I was at home at my folks place where I moved out from about four years ago. Courier turned up at the door with a package for me which I found a bit strange, opened it and inside were two Samsung phones from T-Mobile. Another courier turned up a few minutes later with another package which contained another two phones from Orange. Finally another courier turned up with a package, but when he got to the door he asked me to call the Police, as he said there was a man in a car just off the end of our drive who tried to intercept the package by saying it was his.
Phoned the Police, but he made off before they got there. Basically the thief had used my identity to take out phone contracts, so there were entries in my credit report, apparently the checks the operators use for over the phone sales are pretty lacking compared to in person. Somebody elses details had been used to pay for the phones though, so I hadn't lost any money, but again shows how lack the operators are. With the address it was slightly funny in that I think he had tried to address it to a new house that was recently built over the road and didn't have anyone living it yet, but because it was a mix of address, the couriers obviously knew to go to our home. So this demonstrates just how targeted it was.
The Police were able to trace his car back to London where it had been seen on various traffic cameras. So he had travelled a good 40 miles or so to intercept them and they believe it was part of quite organised fraud. They also told me that phones are the number one item they will commit such crimes on because they are valuable and so easy to move on.