The IRS has recently made it very clear that the owner(s) of an LLC have to file an income tax return in the USA. This applies to LLCs formed in every State, not just in Delaware, so you can't form in another State thinking this doesn't apply to you.
From the IRS website: http://www.irs.gov/businesses/small/article/0,,id=98277,00.html
"The federal government does not recognize an LLC as a classification for federal tax purposes. An LLC business entity must file as a corporation, partnership or sole proprietorship tax return."
What this means to you: