hey sue000,
i am using existing online discussion boards for part of my data collection. things you need to consider include anonymity (or not), the ease of exporting the data to your analysis programme, or, to print it out, without it just looking like text salad, and the ease of saving/logging the inputs.
since you are starting a new discussion board, are you intending to use it as a sort of online focus group interview? if yes, perhaps you should consider a chat tool instead, where dialogue comes more naturally. if not, you might want to consider using an existing discussion with an established community of contributers, instead of building your own which can be very hard.