Travel, and dating sites. Everybody, just stop already.
But neither of these businesses leads to "sticky" customers: people don't travel frequently enough to develop brand loyalty to a travel site, and for a dating site, the ideal scenario for your customers is that they find someone and stop subscribing to your site. This is the kind of business problem that's not readily apparent until you start to dive into the customer lifecycle and personas.
As a result, dating and travel sites are essentially branded experiences where the only difference between many of them is the advertising.
Do I get showered with VC money now, or is there something else I need to do?
"Someone" ought to make a list of the white whale ideas. Not that nobody should ever try one, but I firmly believe that if you're going to try an idea that has been tried a lot already you should go in with eyes wide open.
Or see here: http://en.urbandictionary.com/define.php?term=white%20whale
Ahab sacrifices everything in his mad pursuit. Moby Dick ends up sinking the ship, killing his crew, and Ahab himself. It cost him everything for something that was foolish.
Maybe the moral of the story, try a travel startup, but be willing to pivot.
There are exceptions. That's why I don't phrase this in terms of "never ever try". I say you ought to go in with eyes wide open. Look at what has failed, see why, see if you've got a story that you can do better. It's basically very, very expensive market research that you can get for free. If you then want to put your money on these numbers and spin the wheel, at least you did your due diligence and hopefully maximized your chances.
bwahahahaha, are you for real?
I disagree with this blanket statement. Slack may fix the fact that people are bad at using email at work, but it's not going to let me carry on irregular correspondence with old friends and family, and it won't let people send me receipts, bills and newsletters.
(But, sure, as a blanket statement it misses a lot of important details.)
Let's hope not. It's not the e-mail that needs fixing, it's the whole rest of the Internet. E-mail is one of the few things that have not yet been captured and walled up by private companies. Slack "fixing" (i.e. killing) it would be a very bad thing for humanity.