Basically, you can create your personal do not call list by selecting from a number of organizations ranging from polling companies, airlines, retail, newspapers, political parties, charities, banking, finance and insurance institutions.
How does it work is best explained in their FAQ:
This is an aggressive initiative which will surely get a fair bit of press. There are a few concerns though. For one, organizations listed have no formal agreement with iOptOut.ca, though they are obliged to comply with do-not-call requests by Canadian law.
Oddly enough, the greatest concern is that there is no validation process during registration. This means that the system could potentially be gamed by users registering under different email accounts (i.e. Hotmail) and submit multiple phone numbers that do not belong to an individual.
There probably isn't much risk as the intentions of such gaming of the system only has potential harm to the organizations, but still, one of the primary methods to safe guard against gaming of a system is through a basic verification system - email or other. I would have thought that a service based on privacy would at least implement this level of safe-guard for credibility.
So I wonder if organizations receiving thousands of do-not-call requests from iOptOut.ca will launch a campaign to question the validity of each request?