n=1 is indeed being used. The problem with a larger n is that you get original tweets really often, because the dataset is limited (as much tweets as you can get in one request).
Random example 1: nothing had pleased God to bestow upon you as to participation in physical activity and exercise . Don ' t rain .
Random example 2: sad and terrifying each time . After a quick nap .
http://nlp.stanford.edu/~wcmac/papers/20050421-smoothing-tut...