You stated that you have an LLC. The first thing to do is to make sure that you have a separate bank account for the LLC, enter into agreements in the LLC's (rather than your) name, etc. to maintain the legal firewall between the LLC's activities and your personal liabilities. Please see Beware Your Alter Ego (discusses corporations, but similar issues for LLCs).
Next, make sure that you have appropriate online terms of use (especially as regards the DMCA safe harbor) and privacy policy. Please see How Websites can Avoid Liability for User-provided Content and the post that it links to toward the end.
Once the foregoing steps are completed - once you have taken reasonable steps to reduce liability - it is time to add insurance. I am a firm believer in every business having a commercial general liability policy. The cost is only a few hundred dollars a year. Perhaps its greatest value, given the litigious nature of our society, is that it will cover the cost of litigation in the event that you are sued (which can happen even if you have done nothing to incur any legal liability).
Disclaimer: This post does not constitute legal advice and does not establish an attorney-client relationship.