I don't mean to be critical, but it seems to me that project's data would be more valuable if those who can actually trace their y lines to Ireland were segregated from those who cannot. The latter seem to be a large percentage of the whole, and some folks in that project don't seem to belong there at all.
I went back and checked the DNA database, The vast majority of people listed have either a MRCA located in Ireland or an Irish surname.
The welcome note for the site states
"Despite the surge in the number of surname projects, the Ireland yDNA Project remains popular with people who want to affiliate with an Irish yDNA Project. The project has grown dramatically every year and by January 2010, it has nearly 4,000 members and continues to grow. The Ireland yDNA Project is a useful project for those who are investigating their Irish roots and who may not be sure of where in Ireland their ancestors lived. We co-administrators encourage people to use traditional genealogical methods (where possible) in conjunction with yDNA testing".
I can only assume that those not included in the above criteria do not have direct proof but suspect they have an Irish ancestor. Also it is worth remembering that Ireland has a population of 5M but a diaspora or over 70M.
My Gr Gr Grandfather is listed in Canadian Census records as being born 1802 in Ireland, and paying his own passage to Prince Edward Island, Canada.
What it doesn't show is where in Ireland he was born. I'm sure there are many people with the same information. Family stories say he was born in Cork..and another branch of the family here claims he was from Kerry. Hpefully time will give me a better indication.