AdExcite is legit. Been around since 2009, tech guys were brains behind Interwoven's best CMS technology. They have a proprietary video interstitial unit called the vSlider. Based in LA with another office in Austin. Experienced and trustworthy guys. www.adexcite.com or just email ceo. firstname.lastname@example.org
I think Chitika is much better as compared to adexcite. In chitika, there is no limitation of adding ads units on your site. You can add as many as ad unit is required. They have same adunits like google adsense. There is no limitation ad units sizes.