I was able to combine my accounts without any problem. Actually I created my first account a year back and totally forgot. I signed up using new SFO link recently and was using my new account. Also applied for SWA visa but my bonus credits went to first account. Thats where I called SWA and explained the problem. They did combine my second account into first one. So its possible if you are able to convince that you didnt create two for getting benifits of some promotions...