I would have to agree with the sentiments above, I don't think shared hosting is suitable for such a site. While it may work reasonably well in the short term, there are too many variables involved with shared hosting that you have no control over. You would be sharing your particular server with hundreds of other customers, and there is no guarantee that they will all behave responsibly, all the time. If just one of these other customers was to run a resource intensive script, it could ruin the experience for your customers.
Of-course, dedicated hosting will be more expensive, but worth it if you want your customers to have an enjoyable experience and don't want to be inundated with complaints.
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