I arrived in early May 06 with a return ticket for late September 06 (obviously well beyond the routine 90 days granted upon entry). No one said anything about it: neither the airline or Argentine migraciones as I entered. In early August I got the 90 day extension (100 pesos) at prorrogas de permanencia at the office of migraciones, but I did so only because I was ready to apply for a one year visa. I've never heard of anyone having a serious problem for overstaying a tourist visa...just the 50 peso fine....and no trouble if and when they want to come back.
Thank you for your response steveinbsas. Delta was asking at one time for proof of exiting Argentina after the 90day period has lapsed - I have never heard of it myself but I have heard this story from 2 people already. Just wanted to check facts from fiction. Thank you again steveinbsas for your info.