They are for people who have quit the "real" stuff
After smoking for 15 years it took me just a couple of weeks with one of these (different brand, same idea) to decide that the "real" ones tasted bad. TBH I was probably close to quitting anyway, but these made it much, much easier. And I didn't even use the ones containing nicotine, just the flavoured vapour. Now I puff on one of these every once in a while, but not every day.
I'm not sure I see the purpose of the proximity sensor thingy, other than "Hey, cool, you use one too!" and a bit of a conversation starter.
Do people actually use these in non-smoking venues? I got the feeling that it looks enough like smoking that staff and other patrons might kick up a fuss.
And one last thing, el-reg, whether they actually release any nicotine or not, they seem to help a lot of people get off the fags so are to be encouraged IMHO. Of course the government will get around to banning them sooner or later.