A few things related to the posts above.
- Everyone related to the original series seems to complain about the "low budget", but it should be pointed out that Star Trek's first season budget ($190,635)was higher than Lost In Space's budget in its third season ($164,788).
- Star Trek never ranked above 52 in the ratings, whereas Lost In Space frequently landed in the low 30s.
- Martin Landau being offered the role of Spock. This has been discussed before, and there's evidence to the contrary.
- The TV Guide letter above cites "more than 100,000 viewers...wrote or wired", but what this means isn't clear. Does this include phone calls to NBC? I recall reading that some of what NBC was sent were petitions with many signatures on them, not just individual letters. Furthermore, I doubt NBC created a database to track unique letter writers, so it's possible the hardcore fans sent multiple letters.