Also, advertising and sponsorship don't have to be one-way streets.
For example, by funding Mozilla, Google helped to remove Microsoft's browser monopoly. Since Google's business relies on the Web, that made perfect sense. Now they have their own browser too, which makes things complicated :)
Likewise, Microsoft currently has a dominant influence in video chat, thanks to Skype. It makes sense for Telefonica to erode that dominance, since they have more business opportunities in an open, many <-> many ecosystem compared to a Skype-only one.
Too many companies base their business model on becoming a monopoly in their field ("the next Microsoft", "the next Google", "the next Facebook", "the next Twitter", etc.), rather than allowing interoperability and having to succeed on merit. When this inevitably fails, they leave behind nothing except useless, incompatible APIs. Hopefully this is different :)