I thought I had weighed in on this subject before, but Google can't find a mention of it, so I must be mistaken.
I read in a USA Today article that the Senate has pushed back the date by which Americans need passports when returning from Canada and Mexico. I don't have an opinion on the technical details of the timing of this requirement, but overall I'm in favor of this requirement.
I don't necessarily think that this requirement will increase our border security. Conceptually, however, I think it's good for people to use their passports when traveling out of the country.
First of all, it's easier. After I traveled to a conference in graduate school and my non-passport-carrying fellow graduate students (one in particular) got chastised by Canadian immigration, everyone swore they'd have a passport next time they crossed the border.
Secondly, it makes people think about the fact that they're leaving the US. Maybe I'm being naive, but I think having to carry a passport into Tijuana might make a few people think about the fact that they're entering a sovereign nation with a rich history which wasn't just set up to provide them with cheap booze for a night on the town.
Finally, I hope that Americans who get passports for travel in North America will feel, "Hey, now that I've paid for this thing, I might as well use it." I love America, and I love Americans, but some of you guys need to get out more. Especially now that international travel is not that much more expensive than domestic, people can get out and see the world. And they should -- travel has given me a wider perspective on the world, and I think others could benefit from a more cosmopolitan experience.