I found the blurb they sent me, there is nothing about it not being valid for residents of Ontario.
This offer is valid for new ING DIRECT Clients who open an Investment Savings Account (ISA) with a minimum initial deposit of $100 by December 31, 2005. To be eligible to refer a friend, you must be an existing
ING DIRECT Investment Savings Account Client. You will receive one $13 bonus deposit for each new account opened by a person you have referred as part of this promotion, up to a maximum of 20 referrals (or $260). The offer is limited to one $13 bonus per new account (including joint accounts) and is limited to one account per new client. We will not disclose any information regarding the status of a friends application. Referral fees will be processed within 30 days once an ISA is opened and all account opening conditions are satisfied. You cannot refer a person who is an existing ING DIRECT Client. You also cannot refer a person who has already been referred as part of this promotion. Offer may be changed or withdrawn at any time without notice and may not be combined with other discounts, offers or promotions. Offer does not apply to deposit brokers or market intermediaries. Offer only available to Canadian residents.