It happens - Id say theres quite a few gone now to Eir/GoMo with the deal they have. But a lot of services close off their forum. Not sure if its space leased or paid for through Boards, but maybe they dont think its worth their while to keep open.
Ask AIB,ClickandGo.com Holidays, Boards Deals, Currys & PC World, eFlow, eir, Elara.ie, Gamesnash.ie, Gas Networks Ireland, Komplett, Meteor, Formerly O2 Ireland, QuoteDevil.ie, Social Democrats, SSE Airtricity, SUSI, TheCostumeShop.ie, Three, Vodafone
The above have all closed their forums over the years.