Seems like a pretty haphazard list. Does not convince me to sign up to Quora. The fact that those people are founders or senior people at tech companies does not make their answers any better thought through.

I guess when you ask someone to answer a complex question quickly without giving the subject too much thought, you get a superficial, skin-deep answer - no matter whether they're supposed to be experts in the field.

Indeed, I can remember being told by experts that nobody would ever:

- Use the Web as it wasn't a very "rich" experience

- Do banking transactions on the Internet

- No airline would sell tickets online

These were all predictions by real experts in their respective fields.

Arthur C. Clarke's First Law of Prediction applies:

"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is probably wrong."

All startup ideas persistently fail — until they don't. Maybe it's not the idea that failed, but the implementation?

So the only things that are likely to be impossible are the things that distinguished but elderly scientists don't talk about.

Every topic from Quora posted on HN seems to generate some meta discussion on the websites merits.

It seems that unless you're a twitterbook user then signing up to Quroa is impossible.

Haha, I just woke up and was like... How come I've never heard of twitterbook!!

I got two problems with this list. First, for many items on the list, I can actually come up with examples of successful attempts that tackle the problem. Seconds, it feels like that even the ideas that failed so far look like that there is nothing inherently wrong with them, it's just that no ones figured out yet how to do them well.

It's actually a good list of problems that still need to be solved (and you could be the one who solves them), not a list of ideas you should avoid at all costs.

Ha - I went there to see if Micropayments was already listed. I wasn't disappointed. Though i don't see any sort of e-cash there. I wonder if that's because people have completely abandoned the idea?

Downvote for the suggestion on online groceries - haven't been to a supermarket in months because of online groceries. It works, just needs scale and big bucks.

Groceries depends, I'm sure there not referring to large supermarket chains when saying they are failures. Startups that try and add some value over going to a chains site though seem to struggle.

Anyone know why you cann't browse questions on Quora (or at least it's not clear to me how to)?

It doesn't mention being in beta, so I assume this is the final site...

EDIT: And what's with only being able to register via fb/twitter? I hope this isn't the start of a trend.

Not sure about "Anything involving paying people to look at ads". Lockerz seems to be making a business out of it.