Flickr's API and software hybridization
Part of Flickr's success can be directly attributed to their opening up of their API. After doing so, numerous third party apps and websites were able to integrate Flickr's services with their own. If this were to ever become a growing trend (see Facebook) we'll start seeing more hybridization of web services with client software.
More websites, and especially web services companies, should let 3rd parties create their own front ends to their service. You might have to deal with consumer confusion between who's product they're actually using. For example, someone might not even be aware of the company whose API is being used. They only see the front end and assume that that IS the product. But these problems can be minimized with well drafted contracts on what and how developers use your API. This can include kickbacks as well as attribution and branding.