String:I suspect a geographical split here. Certainly in the UK you'll find a lot fewer people are members as (i) NHS treatment is free in the uk and (ii) there are other companies offering cheaper and/or better cover for travelling and abroad.
They seem to be marketted best (or have less competition) in the US and of course healthcare isnt free so insurance is essential even for daily life.
Im not a member but have a policy with another company for all my travelling involving diving.
Good point String. Same conclusion here in Aus for a different reason: the value for money of DAN SEAP is not quite as clear as with the US DAN. Also, I've had not so great customer service experiences with DAN SEAP (not claims, but other things, getting the policies sorted, getting confirmation of coverage, getting responses to enquiries) and heard some not-so-rosey reports from the owner of my LDS who had to deal with them in a potentially life-and-death DCS case he was assisting with while travelling with other dive pros in the the south pacific. My DAN is up for renewal in Jan and I'm shopping around for another insurance provider.
It seems like a good deal if you're in the US (or North America)...but you might want to look around if you're elsewhere...