Ad spending for online video will grow to over $3 billion by 2012. That’s good news for interactive, classified and entertainment Web sites, but it’s still a drop in the bucket compared to the $70 billion TV market.

EMarketer CEO Geoff Ramsey, speaking about the future of online video at last month’s IAB MIXX expo, explained that the greatest increases for online video ad spending will come from large brand marketers placing TV-like commercials in professional content from large media companies. And that content will be set free from the confines of the TV networks’ destination sites: Programs – includin their ads – will be distributed across the Internet.

Online video advertising will include a variety of techniques. In-stream ads (such as pre-roll) which are currently associated with traditional TV content will increasingly move to online. Product placement, sponsorship and widgets will also be added to the mix.

The full write up plus spending graphs is here.