It is illegal. It is the same as running a poker room in your house.
If you want to run a poker room online, you have to go offshore and then face the same legal battles as everyone else. Is it legal? Is it not? Does the wire act cover it? Etc...
If you were serious about starting a poker room, you had a unique idea as to how to market it, and you had some money, you would partner with someone who is already established. The key would be having the unique market angle.
I think a great marketing angle would be to target colleges in the following manner - set up a site like collegegaming.com . Then offer comps to players - free spring break trips down to the island - have really hot girls there. The rest is history. Somehow I dont think the DOJ would look favorably on a poker site going directly at college kids, but if you're gonna move offshore anyways...