There's a big difference between people saying they'll definitely buy your product and people actually pulling out their credit card and spending some of their hard earned money. You could very easily talk to ten people who are excited about your product and then have only one of them follow through. If you're creating an online store this can be a big problem. You're investing your time and money into this venture and of course you want to know if it will work out.
Before you develop an entire product line try selling just one product. If you can create enough pre-orders then you know you're on the right track and you can develop the rest of the line. With modern technology you can do this on your own site or you could do it on a 3rd party site. One of my favorite products (that I'm literally using right now as I type this) is The Roost. James Olander, creator of The Roost, created a Kickstarter campaign where he raised $189,983 for his initial production run. It was only after that initial success that he created his e-commerce site where he sells The Roost stands year round. He's doing so well he's currently sold out. Clearly he came up with an awesome idea.
You don't need to use Kickstarter. That's just an example. But I do encourage you to try to get pre-orders. You could do this through your own site, Kickstarter, in person, or where ever you find your audience.
I wrote a post on my frustrations with the Terms and Conditions functionality in WooCommerce and I put a contact form on that page. After a dozen emails I knew it was a problem worth solving so I built a WordPress plugin and now sell it through WooThemes.com.
If you get negative feedback that's not a bad thing. You've saved yourself a lot of time. Reach out to those people and ask them why they didn't preorder the product. You'll probably get some really good feedback. Maybe the pictures weren't very good, maybe they didn't trust the website, maybe they liked the product but didn't see enough social proof that other people like it. This all awesome news. Take that back to the drawing board, revise your pre-order page and try again.
If you still can't get pre-order then there's probably a disconnect between you and your audience. Many e-commerce platforms allow you to cancel Pre-orders or not charge users at all. If that's the case you can shut down your experiment and try something else.
If you get a few pre-orders it's an excellent idea to reach out to those customers. They could give you useful feedback and they might give you some great testimonials. Social proof is an incredibly important tool to build trust between you and the random people who find you via a search engine.
Pre-Orders Save Time
In the end you can do whatever you want. I've spent plenty of hours developing software that almost no one uses. I love getting some sort of validation from users that this is a real problem they have and my product is in good solution before writing a single line of code. You don't have to take pre-orders but you should definitely get some sort of validation from your users. And remember that friends and family that say “oh I'd definitely buy that” don't count.