I've just finished reading the Dread manual. While it suggests 5 or 6 players as a "normal" group, and also suggests making a number of pulls before starting for every player missing from that number, I wanted to know what, in your experience, is the minimum number of players necessary for a good game. Can one play with one host and two players, for example?
You absolutely can--I think the best games of Dread I've played all had 2-4 players--but it affects game length and tension in very computable ways. The game gets much slower with fewer people, so it extends the story and the GM can't come out swinging right away. More like Japanese horror than a slasher, if you like.
This suited our group's needs, as it gave us time to have more involved character interaction, draw out the tension, and explore bigger maps so to speak, but I think it requires a higher level of co-operation (in terms of making the game run smoothly, not necessarily in-character cooperation) and prep-work from all parties involved. We're a pretty backstory-heavy playgroup, and it's easier to spend a lot of time on each character's hangups with a small group and more time like this.
I will note also that we usually ignore the injunction to make pulls for the number of players missing, again because we like drawing out the game and taking the time to dwell on atmosphere (Think Silent Hill--lots of time spent wandering through creepy environments, probing the characters' psyches, etc). I think the optimal Dread group size depends more on the type of horror you like than on the mechanics.
.You could play with only 2 players, but part of the appeal of the dread system is that it mirrors horror films where the level of tension and violence escalates as people are picked off one by one. The mechanic of pulling more tiles for each player dead seems to encourage a group of the size they recommend. Likewise, dead players aren't supposed to "chat" with ones still alive. The first time the jenga tower goes down it'll be just you with the remaining player while the dead player sits out.