I always keep an eye on who’s advertising where.
It says a lot about the state of the company and/or it’s growth stage.
It also says a lot about the network publishing those ads – I regularly hover over ads to see what networks are serving what ads on which domains.

With that, three companies that are, based on my scientific web viewing, advertising very actively:

1. Flock - they actually have a great banner unit. Appearing on tech-related or social sites.
2. Disaboom - a network for the “millions touched by disabilities.” They are advertising on any social, news or health properties.
3. Microsoft Live- perhaps the most interesting ads. MS is promoting Live as a dating destination that extends from the net to the mobile phone.

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