As we all know, Google doesn't spend any money in advertising, but relies on word-of-mouth instead to get the message out. However, Google forgoes potential money by "buying" some adwords on its own search engine. For instance, type in "e-mail" and the first paid result links to Gmail. There are lots of other fun tests, such as searching for "web search" (no Google ad), and "news" (Google News is the first paid result).
Surprisingly, this internal subsidization extends to what I would believe to be a lucrative keyword: "VOIP", which stands for Voice-Over-Internet-Protocol, or making phone calls over the internet. Google Talk, which is a very modest VOIP tool that I use right now, is listed 6th in the paid results on the right-hand side. I suspect that this real estate is worth quite a bit, which means that Google is investing a lot of money in the service beyond the costs to develop the application.
While recently I stated that eBay vastly overpaid for Skype, a more full-service VOIP application, Google's internal subsidization of its Google Talk product puts the Skype investment in context. Google is willing to spend a lot of money to expand in the VOIP business, which is some measure of its ambitions in the area.