Truly defeating spam in all its guises (SEO, commercials, daily offers, junk mail) is a pretty difficult problem. How do you recognize cleverly concealed data? Spammers constantly adapt to spam filters and new/pristine communications channels which catch on precisely because they are relatively spam free. Of course, spam filters also evolve, this kind of runaway adversarial co-evolution is what leads to systems which can effectively lie/manipulate perception, or detect such.
1. Needing much effort or skill to accomplish, deal with, or understand.
2. Characterized by or causing hardships or problems.
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.
OK how about I rephrase: I meant "OMG-big-deal-game-changing problems." Difficult is just a proxy for that.
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>
How would you get in and out of the upper (or even middle) floors of a 3000 story building? Atmospherics would be a serious concern at 10 miles up. Sounds like the kind of project the North Koreans would start and then abandon when they ran out of money.