is it possible to brew beer using cilantro?
It's possible, but cilantro's flavor relies on several very volatile flavor compounds. If you end up with the wrong ones, you might end up with a soapy beer.
See Harold McGee's article from yesterday's New York Times about the various flavor compounds and how they affect taste.
I would be very careful about this. As a cook, I'm generally very careful with cilantro for anything but fresh use. If I knew that my drinkers were cool with cilantro flavor, I'd only "dry-hop" with fresh cilantro, and only for a day at most.