It is entirely sensible not to go ahead with a startup if you're not sure about whether and how it would be a successful business. You'll never know for sure, but it makes sense to have a good idea of whether you have a market, for example, before putting in all the work of building the thing.
Putting out your ideas and getting responses is a good way to start. Start an ASK HN post, explain what you're doing, and put each idea as its own reply to your post. Then people can reply to each idea separately, and you'll get a conversation on that.
Remember: the idea itself isn't always fascinating to hear. Basecamp - project management for teams; Posterous - simple blogging. And so on. So don't worry if your ideas get an "It's been done" response. What matters is whether there is room in the market for you, for your price point, for your feature set, for your marketing strategy, and so on.
Putting out your ideas and getting responses is a good way to start. Start an ASK HN post, explain what you're doing, and put each idea as its own reply to your post. Then people can reply to each idea separately, and you'll get a conversation on that.
Remember: the idea itself isn't always fascinating to hear. Basecamp - project management for teams; Posterous - simple blogging. And so on. So don't worry if your ideas get an "It's been done" response. What matters is whether there is room in the market for you, for your price point, for your feature set, for your marketing strategy, and so on.