The main concern with a company like Alibaba selling in the US is the worry that they don't necessarily operate under the same restrictions and conditions that we're used to from other companies. If something goes wrong with Amazon or eBay, we have it close to home and could do something about it. In principal, there's little excuse for not allowing a company to trade, but we'd need to make sure these things were set in place first.
If Alibaba follows the laws of the land, they should certainly be allowed to operate in the United States. Concerns are understandable, but unless a company is showing complete disregard for the laws of the country it is operating in, it seems very discriminatory to keep anyone out. It doesn't seem that Alibaba is doing anything it shouldn't be doing.
Yes I do think the company and website Alibaba should sell in the United States. If there is a demand for them they customers should have the option of choosing to buy from them instead of others on the market. Also the company should be able to get more business.
As we already outsource a lot of our products from China, it'd only make sense that we allow their products to be directly sold to the public. In today's economy, most people are concerned about prices and affordability. While some of the products may not be durable, most people would probably not care as long as it was cheaper.