Brad, how is your brother's situation similar? Menlo Park is the most expensive real estate in the country.
What I mean is that he lives right at the border of two worlds: Meno Park (impossibly wealthy) and East Palo Alto (lots of crime and poverty). There have been murders in his apartment building. He lives on the E. Palo Alto side but in a few short steps he is in Menlo Park. It's similar for us but the other way around: our immediate neighborhood is wealthy but there is a very poor area just at the end of our street.
If it helps you sleep better at night, that's a big consideration. If it lowers your homeowner insurance bills, that's a consideration too. Keep in mind, however, that most of your stuff is probably insured, right? So it's not a huge deal if it gets stolen.
It's not a huge deal but a major inconvenience since I work at home and if my computers were stolen (which are pretty much the most valuable things I own, not saying much but there you go) it would take a couple of days for me to be up and running again even with my offsite backup systems etc. Plus I own a few musical instruments that are essentially irreplaceable...not that much value to anyone on the street, but for me they are priceless; losing them would be like losing a member of my family.
Besides that, your chance of actually being harmed during a home invasion are quite slim in the scheme of things. At least you're considering an alarm and not a firearm.
Not true here -- most of the home invasions in Montreal have involved murder or injury to the homeowners/renters. In some cases they take the person to an ATM and make them withdraw as much money as the machine will allow, then take them back to the house and kill them or tie them up. There was a rash of them (30 or 40) in 2006; I don't think as many in 2007 but you never know.
FWIW, I live in an attached studio behind a house at the end of a dead end street. I recently left my doors unlocked for the week and half I was gone for the holidays.
When I lived in Vermont, I spent five years living in a rented house where I didn't even own keys to the doors. When I asked my landlord if he had a key he just laughed and said "keys are for city people, you don't have to worry about that here." True enough, although some teenagers stole my landlord's trampoline from his front yard one night, and another bunch of teenagers stole some of my stuff from the barn a year later.