Public stream stops after some time


I’m trying to get tweets from the following public stream using twitter module of python 2.7
I create a stream iterable as follows:
tweet_iter = stream.statuses.filter(track = “social”)
and here is my iteration of tweets:
for tweet in tweet_iter:
print tweet
The problem is that it only returns a few tweets and stops returning. It just waits. When I kill the script and restart again it returns different set of tweets and stops again. There is not any continuous stream of tweets. I tried different tracking filters but it always behaves the same. Is this normal?