• Mashable, Friday, October 4, 2013 7:39 AM

Twitter has just filed its IPO, looking to raise $1 billion. In its S-1 document, the company revealed the risk to long-term viability: the loss of user retention. Twitter has seen big user growth over the past few years, going from 167 million monthly actives last September to 218 million at the time of the filing. But the S-1 notes: "We anticipate that our user growth rate will slow over time as the size of our user base increases." Another potential risk to the company: driving users away with an influx of ads and spam.

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