Actually the country that you decide to host the website in might have some interesting implications. Each country has different laws regarding what content can be stored on their servers, some with stricter content laws, others with none whatsoever.
As far as legal issues, here is an incomplete list of things that should be addressed:
- End User License Agreement
- Privacy Policy
- Terms of Service
- Disaster Recovery
- Warranties
- Who will legally supply maintenance
- Duration of license for your hosting, renewals, termination, metrics for adequate service, early termination fees
- Definition of confidential information, best efforts standard
- Information Needed for archival reasons, non-disclosure agreements
- Return of confidential information
- Indemnification from: IP Infringement, liability exclusion caps, users data, third-party infringement (users uploading copyrighted material)
- SAS 70 reports, security levels
- Venue considerations, arbitration in case of suit
And I could go on...so what does this mean? Well, a good lawyer will handle these things with a good licensing contract with your hosting service, a strong EULA and TOS as well as a privacy policy that protects your interests as well as the user's.
It seems like your major concern would be losing confidential data - maybe your #1 priority would be to make sure that you are indemnified from security breaches that occur on account of your service provider.
If you're looking for a good lawyer, might I shamelessly suggest this question/answer: http://stackoverflow.com/questions/613396/632961#632961
All in all, if you're concerned about these legal issues, you have a good head on your shoulders. The price of a lawyer to protect you far outweighs the potential costs. best of luck with your new business website!