There are lots of bad ideas out there.  They're too early.  They don't have a big market.  The business model doesn't work.  They're just flat out dumb.  The key thing when you have one of these ideas is to REALIZE IT'S BAD QUICKLY!!!  And then drop it and run as fast as you can away.  

The really sad thing is when you hang on to a bad ideas for a long time.  You are wasting time and resources by clutching to something that has no long term prospects.  You can be so badly burned hanging on to a bad idea for too long that you might not be able to get back into the startup game.  Your reputation is hurt.  You are completely broke.  You are scarred from the experience. 

The key thing to avoiding this path is to get your idea out there.  Create a Minimum Viable Product (MVP) and start getting it out there.  Share it with friends.  Get it in front of your target audience.  Have people try it for free.  Put it on Kickstarter.  Feedback early is super important. 

The next thing is the hard part.  You want to listen to the feedback, but also be able to filter what's truth versus what's BS.  Lots of amazing ideas had to have sounded like terrible ideas back in the day.  Paying to get into a total stranger's car.  Terrifying.  Paying to stay at a total random person's house.  Creepy.  Paying $25/day for your dog to hang out with other dogs.  Who would do that (me!)??

People will talk bad about your idea.  It happened with Sloane countless times.  You need to listen hard and understand the WHY behind that.  Is the person giving you the feedback not fashionable and wouldn't appreciate the product.  If so, that's totally fair feedback.  Does the person hate spending on clothing, so $34 for an undershirt is insane?  Again....fair feedback.  The thing is that those people are NOT your target consumer, so they really don't matter.  

If your target consumer talks badly about your product, then you need to start getting nervous.  The exact people you think SHOULD plop down money for your product are saying it's terrible?  Not good.  That's the feedback you should listen to.  What are they suggesting to improve the idea?  What are their pain points with the product?  

When people are giving you and your product feedback make sure you LISTEN!  The person who doesn't listen to feedback is the person who sticks with bad ideas for too long.  They think people don't get it and are dumb.  They'll eventually find the market for it.  Often that eventually never comes.  

Be open.  Listen.  Learn.  Developing your product is all about iterations to get it to the best place possible.  Just make sure you are listening and learning from the RIGHT people.