You can see my comments about Memory Foam Factory Direct in post #2 here.
I normally don't spend much time researching Ebay sellers because the end result is so often the same (I wouldn't buy from most of them) but since you are the second one to ask about them ... I thought I'd connect a few dots in this case based on some notes I have about them and some online research.
The listing has two phone numbers. One is the number on the listing 1-877-493-6978 and the other is the number for their sleepmemoryfoam store which is 1-800-718-0468
They say they have a local store in their various websites ..
We also carry many of the name brand mattresses you see in stores. As our memory foam beds have grown in popularity with our local customer base we decided to launch a website that prominently features our memory foam products at the same great prices our local customs have enjoyed for years.
but a search on the various addresses they have listed in various places on their sites and around the web leads to warehouses, private homes, or incomplete or incorrect addresses including ...
The difficulty with these vendors is that the feedback comes very quickly and are written in the excitement of "the deal" and most consumers have little idea about how to determine what is a good quality mattress. In addition to this ... return costs on a mattress like this can be more than the cost of the mattress if you make a "mistake".
I could probably do more research on them but I have enough question marks and doubts that I would hesitate to buy from them.