How do you validate an idea before you build it? Sell it

In my case, I used a few different marketplaces, but I might also recommend competitor's forums.

Just go to where your audience frequents and sell them something, and if they pay for it, build it.

Some of this might be considered spam, but I would imagine if you did a bit of research or attempted to explain how you add value in some way: I'm sure people don't mind direct emails or direct messages (if something exists)

With that, I'd recommend stuff like linkedin/twitter etc to find relevant people in the industry you want to sell to and work from there.

I worked my ass off, and in the end when it was released, it turned out more than 90% of people only use the base product.

I think I'm still mentally recovering from that one and it it was the initiator for the spoiled relationship with the co-founder.

It takes courage to contact people, ask for a meeting and tell them what your plans are.

But it beats spending months working on something no one wants.

And every time you do it, it takes less courage.

After reading all the great posts by Jason Grigsby (http://blog.cloudfour.com/) the problems with sending one-size-fits-all images to mobile and tablet devices was obvious. Additionally, most existing solutions require you to pre-scale/crop multiple versions of the same image which is tedious and labor intensive. Even the proposed srcset attribute and picture element have this requirement.

Next, we looked at any existing players in the space and found that a few where starting to crop and getting traction which further validated our premise that people where looking for a robust solution.

So, we considered it worth at least building an MVP and will soon be looking for interested parties to try it out (drop me a line if interested - and yes, our site is butt ugly).