Top 4 Unsolved Computing Problems

My father-in-law recently asked me what I think the big outstanding computing opportunities are.  I think these are some of the top problems.

1. SPAM (Email and Web comment) - Of course there are solutions here.  But I think there is still opportunity for someone to do for spam what google did for search around 1998.
2. Image Serach - Some approaches are getting off the ground. Gazopa is interesting, the example images work beatifully, but uploading your own images the results aren't as good.
3. Video Search - Lets stick with image search for now...
4. Naturual Language Interface - The holly grail of computing. Would in theory make computers usuable by anyone who can talk.

What do you think are the main unsolved problems?  Leave a comment and let me know.