I know the producers of Lost have always denied they will use the "it was all a dream" to end the series but there has been a few "disturbing" events throughout the series that makes me wonder for example:
In "Born to run" on the door to the x-ray room it says "IMAGINING" instead of IMAGING. This may have been just an error but I wonder.
When we first see Frank a poster behind him says "Carribean Dreams."
When Locke in the FST is applying at the employment office we see posters behind him saying Dream Job and something like follow your dreams or something similiar. These all may just be "Easter eggs" but I wonder.
Of course we've had many sequences that turn out to be a dream (or was it a dream within a dream. But the final straw was when I froze the scene of Daniel's notebook and read his calculations and I saw his graph featuring real time real and "Imaginary time". So I wondered. Is this all or part of someone's active conciousness?
I really hope not. The dream sequence is one of the most hackneyed plot device in history but that hasn't kept some otherwise good stories from resorting to it. (Examples: Twilight Zone had used it a few times, Stephen King, and maybe the most famous "St. Elsewhere's famous "snowglobe moment".)