The CBC just ran a story on what happens to defunct bank accounts in Canada.
Apparently, if an account is not touched for 10 years, the bank with which the account is registered transfers the funds to the Bank of Canada. They, in turn, keep it for 40 years (100 years, if there's a ludicrous amount of money in it) before appropriating the funds.
The BoC has a
search form for unclaimed balances. Much fun! I've already found $20 for my brother (and told him as much). ;)
ETA:
Here's the link to the CBC story (runs 2:20).