It's never a good idea to ask this question. Even worse: Asking someone if this is a good or a bad idea. The question itself doesn't hold any value at all. Neither do any of the answers you'll get.
The only thing that asking someone this question will lead to are misconceptions and confusion.
Most people will tell you that it's a good idea because that's what we know you'll want to hear. We're all just lazy. We don't want to argue. We don't want to get into a fight. We don't want to waste our time. So we'll tell you what you want to hear. It's a lot easier. And we all love easy.
Other people, mostly called mentors, advisers, consultants or coaches will constantly tell you conflicting things. One person might say this, whereas someone else might tell you something else entirely.
The end result being that you're left alone, even more confused about things than ever before.
As a matter of fact, there are no good or bad ideas. Your initial idea is just one piece of an entire idea puzzle. You need to start collecting these pieces. It's a web of ideas ready to be untangled.
Some people call this execution. I call it idea puzzle. That's what it really is all about.
It doesn't work on a piece of paper. You need to get out there, test it and see what works and what doesn't. Just like a puzzle. You need to test and see whether or not the pieces really fit together.
Execution is nothing else than hundreds of ideas combined to make your initial idea work. And that's the really hard part. Being creative, coming up with all sorts of ideas and seeing whether or not they fit.
That's where you need to make your brain sweat.
So instead of wasting your time asking people (and yourself) this useless question and trying to predict the future, get on the market as fast as possible, collect the pieces of your idea puzzle and start untangling your web of ideas..
Looking for inspiration?
I put together a list of startup ideas that cost less than $100 to build. You can join here: $100 Startup Ideas
[Related: I stopped giving a shit a long time ago]