For just one example, consider airline staff. Some Canadian airlines have already banned employees from using pot. Obviously, the general public doesn't want to fly with pilots that are high in more than one way. These airlines also have to operate in countries, like the U.S., where their employees could be detained or expelled for even admitting to have used pot in the past. Being able to look foreign gatekeepers in the face and deny having ever used a product that's legal in your native country is now a necessary job requirement for some.
On the bright side, we could finally get some quality data on the health impacts of pot, now that trials and surveys can be done without potentially incriminating anyone. Like practically every other fun thing in existence it's probably very bad for you. We just don't know how... yet.
Canada taxes alcohol at a rate of over 50% in most provinces. The initial tax rates for pot will be much lower, but should increase steadily year-over-year. Alcohol taxes continue to rise every year. This is going to be a huge cash cow for the Canadian government, and I can't imagine other countries not wanting to get in on the action once they see how much Canada will be raking in.