The biggest problem: The overwhelming dearth of original ideas.

If you have the ability and time, I would focus on AI software and robotics to provide healthcare. I heard a quote on Bloomberg saying that we will be losing a million doctors by 2020. The cause? I didn't catch that part, but my guess is retirement or because the field is no longer viable between the high malpractice insurance premiums and low reimbursement rates. The coming generations will have less access to doctors at a time when they need them the most. That's an amazing opportunity for those who can deliver healthcare at scale and at an affordable price.

The slowing pace of innovation as measured by time saved. http://www.nytimes.com/2016/02/21/magazine/are-we-doomed-to-...

The trend since the 1970s in which the wealthiest reap the majority of any economic growth and hold more and more assets while the middle class and poor have seen wages stagnate as compared to inflation or shrink, and an increasing gap in wealth. http://www.cbpp.org/research/poverty-and-inequality/a-guide-...

The trend of finance as an increasing part of GDP and shareholder return being seen as a better proxy for economic success then long term growth, investment in durable assets, and infrastructure, especiall when much of the value finance and immediate shareholder returns add are questionable. http://www.washingtonmonthly.com/magazine/novemberdecember_2...

Define "we". We on HN? We, the human race?

For the human race: Safe water, war, climate change, and better access to space are probably on the list. The insane US political climate might be up there, too.

For us on HN: Anything that you can do to make a dent in any of the above problems. Also, internet security is completely broken and needs a total re-think and re-do. We need safe access to the world's information for the several billion people who are not yet online. (For that matter, we need safe access for everyone else, too.)

We as human race, but more specifically technology folks

Edit: also, reasons for why listed problems are in higher priority than others (in your opinion), and potential solutions would be very interesting to read.

Social incompetence in a broad sense (human inability to cooperate sustainably, express emotions & desires, discuss constructively, etc).

Financialization of the economy and rentier capture of value/profits. There are six billion people who are waiting to be brought up to the average American's standard of living but have no path to it. Vast investments in housing, education, transportation and healthcare are needed, many times more than what even China has attempted, but this cannot happen as long as ROI is higher in the financial sector and increasing levels of debt prevent forward movement. Debt forgiveness and plain old money/land giveaways need to come back in style.

The ability to create very affordable, but quality shelter/housing. Cheap & effective materials, a solid, reusable design, small footprint, easily replaced components, etc.

Off the top of my head, this might look like:

Cement block housing, very limited plumbing (with ability to have a pitcher pump at the sink), composting toilet, some kind of simple fold-out cot/bed/hammock, small furnace/woodstove?, etc.

Make housing so simple & affordable that every single person can have a safe place to stay, even if that place is without luxury.

Good luck getting the government to approve that. (If you're talking about the US, anyway).

I think basic income and what the world is going to do with the unskilled labour that comes from increasing automation is the problem of our lifetimes

Environment Environment Environment.. restoring our only home to a sustainable place, like it was before few centuries back, before the industrial revolution and the population explosion.

Education. Any other issue can be solved by having a better educated population.

We're relying on fossil fuel to produce fertiliser for the vast majority of Earth's food.