From the lawyer

If you operate a business -- whether it is online, offline, out of your home, or out of your office -- you may be required to have a business license. Your county or city can provide you with this information. You may not have to have a corporation, LLC, or Limited Partnership, but you may be required to register a fictitious name affidavit with your local government. In California, ANY venture done from your home that has any revenue (that doesn't mean profit) is required to have a home business license through your county. If you sell a tangible product across state lines, you may be required to collect sales tax in certain states. Your state revenue department can answer this question.
If you pay any one individual or business more than $600 in a calendar year, you are required to send them a 1099 and file a copy of the 1099 with the IRS. You may issue 1099's for any amount, but when the amount hits $600 it becomes a requirement. Caution: Any time you issue a 1099, you better be able to show where you reported it as income on your tax filings. You may also be responsible for franchise and business taxes in your state or province. Each state revenue office can provide this information, and is usually on their official website. If you ever ask one of your members for a Social Security number or Tax ID number, you are required to provide them with certain IRS forms that show exactly why you are asking for it and that you are in compliance with the Privacy Act of 1974 and The Paperwork Reduction Act (go figure). If your program is located outside of the US, you may be required to provide a different form of 1099 to report foreign income to a US taxpayer. The fines and penalties for failing to comply with these laws are steep and harsh.
ANY webmaster -- regardless of legal standing (sole proprietor, partnership, corporation, LLC) can be sued by an individual or group of individuals for fraud if you fail to pay the members of your program. There is no guaranty that they will win their case, but for fraud suits, you are looking at no less than $50,000 in legal expenses to defend it and legal aid does NOT help in these cases.
As for tax deductions in the US, you may only deduct that portion of your equipment, supplies, home office, utilities etc. that are in direct proportion to the actual use of those things for the business. For example, your home office has to be exclusively used for the business and not for personal use to be eligible for deductions. The same goes for your internet access, portion of utilities, computer, etc. If you use any of these items for personal as well as business use, then only a fraction is deductible and you must have written records to support it. Also, some online businesses are not qualified as businesses and considered "hobbies" by the IRS and thus you are not eligible for deductions. You must also show a profit in a certain percentage of the years you operate the business or your deductions will be disallowed.
I'm glad to answer general questions, but cannot answer specific questions for specific individual cases unless you reside in Nevada, Florida, or California (where I am licensed). The information I have provided is basic information that applies in almost every state with little differentiation, and the IRS information applies no matter where you are in the US.