Difference between three tier vs. n-tier

Question

I just came across the following sentence:

As the industry has moved from a three tier model to n-tier models, the object relational impedance mismatch

Answer 1

Where is that quote from? What industry are they referring to? I would have to imagine that this has something to do with SOA because that is the only thing that makes sense for this kind of statement.

Most people that I have heard who make this kind of statement believe that in a service-oriented domain each service is somehow its own tier. I disagree as most of the time these disparate services can be logically grouped into the common three tiers anyhow (presentation, logic, and data). But again, its all pretty subjective.