Press releases continue to be a great way for businesses of all sorts to get their message out about myriad things going on with their business, and I would tend to think that an online business would be equally benefited by doing a press release as any other type of business would. Granted, at the end of the day it still comes down to the product, credibility of the business, and strong business acumen for any advertising effort to provide any real benefit to the company.
As for backlinks I cannot refer to them. The press release should be simple, concise, direct and to the point, and should have the relative affect of causing someone to dig a little further into the nature of your business. Only that will cause anyone to curiously seek your product, service, or other offering out.