A great-grandparent or even a great-great grandparent from Italy used to be all it took to guarantee Italian citizenship. A surprise decree has now changed all that, making it much harder for those with Italian ancestry to use blood line as a pathway to become Italian.
On March 28, the Italian government tightened regulations for claiming citizenship by jus sanguinis, or descendent blood line, effective immediately.

Basically you now need an Italian parent or a grandparent who was born in Italy, or an Italian parent who lived in Italy for at least two years before you were born, to be eligible. This is a major change to the citizenship law, and caught everyone by surprise.