Matt & Jim,
I agree that a fulfillment service would be a good service addition for

(having an established base of a couple thousand cart customers). From a cart-competitive offering standpoint, it certainly would be a differentiator and would be another revenue stream.
I also agree "non-compete" only makes sense.
However, I know the distribution/logistics world and the only way for them to get into fulfillment profitably (and economically for customers) is to be operationally excellent. From what little I know of the

folks, they have a lot of technical skills and web business smarts, but I'd be VERY surprised if any of them have the required experience, knowledge and competencies to run a 3PL that can scale.
Running your own fulfillment effectively is a COMPLETELY different thing than doing so for a couple dozen small e-tailers (let alone any large scale operation). There are major issues of process, product, systems, e-tailer size and personnel compatibility. In short, Third Party Logistics is a whole profession unto itself...and not something you can just "get into" successfully.
So I could be wrong, but my advice is that if you're looking to outsource, check into other options out there in the market. I don't think

will be offering a reliable, quality fulfillment service at a good price anytime soon.
Frankly, I think a better "play" for

might be to quantify demand among their cart customers and then contract with a firm that is already successfully in the 3PL business, playing the role of deal broker (demand aggregator). That would save the 3PL the trouble of finding and selling a bunch of little sales and maybe get them to a volume that made it worthwhile. It would also save

the capital outlay, ramp up problems and operational headaches of actually being in 3PL biz...and they'd still get a cut (commission if you will).
Anyway, that's my two cents.
Ed