Everyone has different tastes. It also comes down to what kind of theme you're going for.
I've heard several suggestions about having multiple grids/communities/etc. but that's kind of going against the theme of isolation. If you're doing Battlestar, and the central theme is "this fleet represents the last survivors of mankind", then it gets a little jarring (for me) if you're constantly running into other survivors. Occasionally it's fine (like in the new BSG when they came across Pegasus). But do it too often, and you're disrupting your central theme.
Now it would be totally valid to structure a different theme where your goal is "round up other survivors" or "become a bastion of civilization where other survivors can congregate" or whatnot, but those are fundamentally different, not-so-isolated themes.
Asking what kind of playerbase the setting can support is a totally good question. A Battlestar fleet with thousands of people is totally different than a single plane crashing on a deserted island.