To be fair, they never said there would be 120 beers. They said:
"We are dialling up five bars for the event with [b:7r73a98k]120 taps of craft beer from ourselves[/b:7r73a98k] and invited breweries from Ireland."
Since Brewdog don't have anywhere near 120 draught beers at any one time*, it's clear they must mean multiple taps of each beer spread across 5 bars.
Much like a Superpub in Dublin might have 5 floors, multiple bars on each floor, 50 odd taps but only 5 or 6 actual beers on tap.
There's more than enough choice there for me but then again, I'm a glass half full kind of person. I also know that 120 beers would be far too many for a single day event.
*Pretty sure that no brewery on the planet possibly could.