The service, called Wave, will erode the distinction between the various ways people keep in touch on the Web and eliminate the need to use multiple tools to do so, the company said. Google previewed Wave at its annual developers conference in San Francisco. The free service won't be available to the public until sometime later this year. Additionally, Google intends to incorporate some of Wave's features into its other services like e-mail and documents. Wave's users invite others to join their "wave" about a particular topic so they can follow...