They go on to define their terms: "breaking down traditional data center technologies into their core components" -- very little to do with what we think of as "data aggregation."

So, I wouldn't exactly call it ironic. More... homophonic? Homophonically ironic?

The full sentence is even better. "We’re big believers in the value of disaggregation – of breaking down traditional data center technologies into their core components so we can build new systems that are more flexible, more scalable, and more efficient" (at aggregating user data).

I don't know why you think this is ironic.

First of all, I don't know if FB is really the biggest data aggregator. Even if it was, what does data aggregation have to do with aggregation within the data center? Maybe you dislike Facebook the app or "the business model" or whatever, and that prevents you from thinking straight about the implications of this announcement.