Sandbox and Sub domain

[nextGoal100kVisitors]

Sandbox is just a theory, but let's say it's true. How does it work for sub domains? For example, let's say that I launch www .someWebsite.com and it's up for 4 months; the site is out of sandbox. If I launch forum .someWebsite.com, is it going to be sandboxed again? What if I launch forum .someWebsite.com first and then www .someWebsite.com?

[Dominic]

I'm sure someone will correct me if I'm wrong - but I thought the sandbox was applied to links to new sites - thereto effecting sites.

If so I would say go incrementally in adding links and get them one each from various domains rather than site wide from few domains to avoid the sandbox wrath and once the site is more established adding a subdomain shouldn't be a problem.

[nextGoal100kVisitors]

... once the site is more established adding a subdomain shouldn't be a problem.

I seem to remember that subdomains are treated as different domains by SEs. So, following that theory, subdomains need to establish themselves separately? But, if so, if you have like forum .someWebsite.com, www .someWebsite.com, and directory .someWebsite.com, then you have a whole lot of work to do to establish all these. That doesn't seem right.

Anyone familiar with this particular issue? Enlighten me!