I agree with the comments made by Expatriator.
I also know of several Americans, Canadians and Austrialians who have majorly overstayed, that is, overstayed several years without running into problems.
I have overstayed on several occassion and had no problems re-entering or applying for my current residency permit.
Unlike the U.S., where every person’s exit from U.S. territory is registered in a database, the rules about overstaying don’t seem to be applied here as strictly as in the U.S. where you are automatically barred if you violate terms of your visa stay.
To be absolutely safe and keep risks to a minimum , of course, you could follow all the rules exactly to a T.
I seriously doubt whether your friend is going to be in trouble. After all, you are not a minor and your friend does not have authority over you.
My visa in Spain is running out of time but unfortunately I need to stay 2 to 3 more weeks (I am not an EU resident). I can not get extention since it is an invitation visa by a friend.
I have never heard of anyone being fined at the airport.
I overstayed my visa in order to marry. Now, this is the catch. If you are from a country whose citizens are required to have a visa to enter Spain, when you go to apply for marriage, you might run into problems because the civil servants at the Registro Civil will verify your visa status here. I have heard this from a Spanish friend whose partner was North African. When they went to the Registro Civil to apply for marriage, his visa status was verified. In my case, I didn’t need a visa to enter Spain, hence they didn’t need to look at my visa status.
If you leave Spain on a flight from Spanish territory to a non-Schengen area, your passport will bear an exit stamp that shows the date that you left Spain.
If you write Spanish, you can go to http://www.migrar.org run by the Spanish Red Cross to present your questions. There are several immigration attorneys (volunteers) who review questions and answer them, citing the relevant legal codes.
Just a caveat, I’m just going by my personal experience… and I don’t know what has happened to others..
Good luck!