This is a hard question to answer. I work on a lot of side projects in the form of open source libraries and whatnot. It's possible that any of those could blossom into a business, but I've never really pursued many of them.

As for other business projects:

* I tried to resell knives and other camping gear on eBay once. I called it Wolfcastle Munitions. That was a disaster. I'm not built to do retail.

* I had an idea called Project Mothership that was going to be Rails hosting (before anyone was doing dedicated Rails hosting and much like what Planet Argon became) but I abandoned it after I realized that I'd lose my mind if my job became network operations management.

* I wanted to do a climbing sight called Microbomber that would list and categorize climbing routes across the world with photos and reviews and whatnot.

* I also thought about making custom gloves and coats for hardcore outdoor activities (wilderness hiking and skiing, etc). I have a near impossible time finding gloves that fit me well and are legitimately waterproof, and I've still never owned a winter coat that I've loved. I was also going to use the name Microbomber for this effort.

There are plenty more that I've long forgotten.

But, all of these ideas (except the first) I only spent very small effort on. I like to put small efforts towards a lot of ideas and then see what catches. That way I don't spend a lot of time and effort that is later wasted. Knowing when to abandon something and when to dive in is the hardest part, but it's essential. Call it what you want: intuition, savvy, or instinct. I just call it seeing the world objectively and not overvaluing every little idea you happen to have.

Do you feel like you truly tested any of these ideas? If so how?

I have built something that I think is good, but has not taken off. I don't think it is a bad idea, I think it is an untested idea. I would hate to drop it without anyone ever seeing it.

With a lot of effort I think they all could have been successful. But when you have to work your day job to make a living, you need something you can bootstrap on the side without investing huge amounts of unrewarded effort up front. That's why I like to start a lot of things and then see what happens. Sometimes I give up on an idea simply because it becomes uninteresting (e.g. retail). With both Gravatar and GitHub, it was almost immediately obvious that they were ideas worth pursuing. They got people excited, and I could easily gauge the interest by tracking signups. If you're not seeing signups, it means something is wrong and you'll have to decide how much effort you're willing to invest in order to fix that something. Without knowing the details it's hard for me to give any more insight.

Have you tried Oakley gloves? Some are fairly waterproof (and yet breathe), and they seem durable and well fitting, at least to me.

I've got 11 out of 12 that are failures. If you want to see them ask. And a few that have been winners. I'd build products whether they made me money or not--we're at a lucky time in history when the thing I (we?) like to do as fun and as a hobby is sometimes also really commercially viable.

Yeah, that's what makes the internet a great place to start business. You don't have the risk to lose tons of money if your business falis.

That was a great topic to discuss. I've created an extra HN thread, Side Projects Gone Dealpooled, for those of you who are interested: http://news.ycombinator.com/item?id=1772903

I really like this question! How many failures does it take before a success?

None. It is not necessary to fail to succeed.

If you think, the idea is good, give it a shot. See what's the response. If it works, continue else quit.

Key thing is to know when to quit.

That is the key thing. I think perseverance is important, but perseverance through iteration. How long would you give a new web startup to reach 1,000 users? 10,000 users? before you considered it a failure or necessary to quit.