There was a thread on UK business forum a while back about a chap who went on Uk DD with an ecomm business (can't remember what exactly, something to do with outdoor gear, tents or whatever) and got slaughtered by the dragons, one of which was slagging him off for not 'owning' the ecomm framework and using an off-the-shelf one instead. Something along the lines of wanting him to spend £10k of it on that or it wasn't a real business. Anyway, the thread ran for a few pages before the chap popped up himself and thanked everyone for their input - he was an active forum member for several years.
He described the process during filming etc. and explained his reason for doing it - exposure. His sales increased a stupid amount immediately following the airing, not sure if they've maintained that - didn't really follow up what happened as the show isn't about investment or what happens after. A few become z-list successes from the investment, but we don't really hear anything about the inventions or products in the mainstream that often after it's over.
What you have to remember here though, is that this is a TV show - it's made by a production company to sell to broadcasters to gain viewers, so it's for entertainment / advertising purposes only. The content, although reasonably irrelevant, is entertaining and good enough advertising platform that it works in multiple countries - need I say more. It doesn't matter if people get investment or not really - those who are already successful (or will be) are there for the exposure, and a free 10min "advertising" slot on prime TV is worth how much?
I don't know what your networks over there charge for that sort of thing, but I can tell you that's not cheap here in Uk and to make it better it's on a fucking BBC channel!
As someone who spent over a decade in TV production (including advertising) I think I can say with some confidence what this show is about. (concidentally I did a project with one of our previous Dragons just a few years ago, nothing to do with the show - other media stuff, but he was on it at the time.)
As to what you can expect - it will be ~2hr filming cut up & edited into 10mins for good TV. Expect your valid arguments to be edited out if the producers want you to look a prize twat, or edited in a positive way if they like you. Trust me - I know this from experience
You know this yourself Norbz as someone who's been involved in this kind of production shizzle before (well, ok audio production), but I'm just trying to cement the point here about the purpose of the show, I know nobody here needs telling of its true value, I guess the thing to do is see if you pal up with the producer / team for best results. I'll see if I can dig out that other chap's thread - made for quite an interesting read.
Wishing all the best in getting on there - that would be fantastic!
edit: To say Dragons Den is not a show I've had anything to do with just to be clear.
.