This post is actually a bit of an experiment. We're trying to find better ways to get prospective startup founders (which includes many of us in the HN community) in contact with problems that really ought to be solved. We have lots of different ideas for ways to do that, but a list of ideas seemed like an easy one to try out first. Please let me know if you can think of a better/different way of accomplishing this goal!
As to why we're doing this -- more great startups is good news for YC, even if they don't immediately apply to our program. We'd much rather spend our time trying to grow the ecosystem as a whole and maybe capture a small part of that than trying to immediately monetize everything we build.