Heh. They may be the oldest, but that doesn't mean they're still around.
For the top 10:
#1 - Bankrupted, bought by private company.
#3 - Pretty sure that wasn't the original think.com
#4 - doesn't resolve!
#5 - Bankrupt, bought out by Intel
#6 - Merged, domain doesn't resolve (?)
#9 - Merged, but still around.
#10 - Acquired, renamed.
The next 10 fare better, but not by much.
Also notice how most of the big players in the aerospace industry are there, but the biggest software company isn't (Microsoft.com)