Faction Response

It is stated, by Madison, in Federalist #10, "By a faction i understand a number of citizens, whether amounting to a majority or a minority of the whole, who are united and actuated by some common impulse of passion, or interest, adversed  to the rights of other citizens, or to the permanent and aggregate interests of the community."

       This describes a group of people united by a common interest. Whether it be a goal or common interest,it is a group of citizens who are trying to do something.

Questions

1. Would a group of protesters be considered a faction or does there have to be certain characteristics or numbers?
2. Could politicians create factions to back their campaign?
3. If a large group of illegal immigrants were united what Madison described as a faction, would it be considered a faction, because Madison clearly uses the word citizen multiple times?
4. What happens if factions become to large and powerful and start to hurt the welfare of other citizens?

My definition: 

A faction is a group of citizens, who can be minority or majority, that are united by a common passion or goal.
Today factions could be used to persuade voters or politicians in congress to vote a certain way.