I must say I don't completely understand his point. What comes in the place of messaging middleware such as RabbitMQ?
Even web "2.0" applications still need to send each other messages, both synchronously and asynchronously. For example, to trigger backend work that should not be handled on the web server, and receive the results. Or to notify when changes in data happened.
I guess it depends on the specific architecture, if you use something like Mongrel2 messaging is used for everything, even for routing HTTP requests and responses to the processes/servers that handle it.
Also, hasn't it always been the case that a lot of web applications communicate with the database directly to fetch information? What's so "web 2.0" about that?