To me, it sounds like one of two things. What immediately comes to my mind is crappy dealer prep/detail. An inexperienced or less than caring 'detailer' runs a rotary and you wind up with swirl marks. When you first took delivery of the vehicle you may have not noticed due to lighting or a finishing product, like certain waxes, that fill the swirls temporarily.
The other option, is that you may be responsible for the swirls depending on your washing methods. I think that this would be far, far less likely. Automated car washes, dirty towels, dirty water, can swirl the finish, but you're more likely going to see scratches and marring rather than distinct swirls.
The good news is that it is more than likely fixable, and if done correctly, will look better than ever. I personally wouldn't trust the dealership to correct the paint. I don't trust them to clean my vehicles in any way. Find a professional and reputable full-time detailer to correct your paint. If it's a black Tahoe, it probably won't be cheap (couple/several hundred, it is time consuming to do correctly and the size of the Tahoe doesn't make it any quicker). You might attempt to get the dealer to reimburse you for it or do something for you, but I would think that will be an uphill battle. Good luck and let us know how it turns out.
If you want to know way, way more about taking care of this kind of thing, head over to Autopia.org.