Multiprocessing useless with urllib2?

I recently tried to speed up a little tool (which uses urllib2 to send a request to the (unofficial)twitter-button-count-url (> 2000 urls) and parses it´s results) with the multiprocessing module (and it´s worker pools). I read several discussion here about multithreading (which slowed the whole thing down compared to a standard, non-threaded version) and multiprocessing, but i could´t find an answer to a (probably very simple) question:

Can you speed up url-calls with multiprocessing or ain´t the bottleneck something like the network-adapter? I don´t see which part of, for example, the urllib2-open-method could be parallelized and how that should work...

EDIT: THis is the request i want to speed up and the current multiprocessing-setup:

 urls=["www.foo.bar", "www.bar.foo",...]
 tw_url='http://urls.api.twitter.com/1/urls/count.json?url=%s'

 def getTweets(self,urls):
    for i in urls:
        try:
            self.tw_que=urllib2.urlopen(tw_url %(i))
            self.jsons=json.loads(self.tw_que.read())
            self.tweets.append({'url':i,'date':today,'tweets':self.jsons['count']})
        except ValueError:
            print ....
            continue
    return self.tweets 

 if __name__ == '__main__':
    pool = multiprocessing.Pool(processes=4)            
    result = [pool.apply_async(getTweets(i,)) for i in urls]
    [i.get() for i in result]