Will your customer see your value proposition as essentially provided by what your webservices partner is doing? If so, rethink your strategy.
When I lived in Morocco, I developed a small business consulting project for Catholic Relief Services. The small companies we worked with were generally established by skilled tradesmen who were very good at a particular skill and had managed to build up a team around them. Often, these tradesmen wanted to bring on partners to handle the customer relationship. We always counseled against this, since the partner would own the relationship and therefore the business. I think similar advice may hold for building a business with web services.
If you are building a business with web services provided by others, they should not form a key component of your customer interface. If they do, you are in trouble. Your value proposition may be obscured, and your ability to deliver critical services may be hijacked.