He means world hunger, building spaceships, developing new sources of clean energy, etc.
I'd rather have spaceships AND spam than no spaceships and no spam.
I don't see lack of spaceships causing hardship, so that's really more of a definition #1 type of thing. Society built spaceships in the 60's, contrast that against the effectiveness of a spam filtering system built with hardware, software, algorithms and statistical inference techniques available in the 1960's.
While I appreciate and admire the work put into into accomplishing space fight, the existence of manned spaceships really doesn't contribute much to my existence, whereas spam sucks away a bit of my life, every day.
To Stephensons point, which he makes in the video in the link, he really means dreaming up and solving big problems. The example he gave was building the worlds tallest building. I'm paraphrasing him here: <paraphrase> Typically accomplishing the goal of building the worlds tallest building is measured only in contrast to the current record holder. So when people aim to set this record, it's only incrementally bigger. If you actually do the research you'll find that it's possible to build a building 20x taller than the tallest existing building. Why aren't we thinking on that scale?</paraphrase>