talking about online start-ups, I need to mention the most popular website in my country--Taobao. It can possibly be the largest web site for online shopping in Asia, and almost all my friends had ever purchased something from Taobao.
It is obviously that Taobao is a successful platform operated by Alibaba Group, with more than 370 million registered users and 800 million products, all I can say about this online shopping mall is "wow"!
sellers can post products on Taobao through a fixed price or by auctions. buyers can judge the seller's credit from the selling prestige and the comments from other buyers.
one of my friend opened her "store" on Taobao half year ago, base on her experience, it wasn't complicated to become a seller, you have to follow the rules,regulations and understand the services and features that Taobao offering. for example, the payment platform-Alipay and the chat program named Aliwangwang. The payment platform is a preferred payment solution for transitions on Taobao; Aliwangwang, which is more important base on local culture, is more like MSN messenger or Yahoo messenger. usually online shoppers love to chat with sellers about the size, shipping or the price...so many of the sellers have customer service team to handle such things. Of course, when you need a team to chat with customers, it means you business runs really well^^
couple of the difficulties my friend faced as a start-up were : you need to have some skills to decorate you webpage, at least make you store looks pretty; also photoshop is needed, models and photographer are musts. sometimes, when customer bought products from you store, they can hardly remember your brand, instead, they will just say they bought them from Taobao...so it's not easy to build brand image.
anyway, it seems, searching on Taobao has already became part of many people's daily life, my friend says the first thing she does when she opened her laptop, is turn on the facebook, login Taobao, and then check emails or read blogs...so i truly believe web entrepreneurs have lot of chances by doing similar business.