The sandbox has triggers that put you in and triggers that get you out. What those triggers are is the Million dollar question that can only be answered by a few souls at the Googleplex. Notice that Matt Cutts site had no issues with the sandbox.
Voodooman, if your intention is to not make any reciprocal links, then you may avoid being put into the sandbox. Not sure what happens if you manage to get only one-way links. But as you said, if you don’t have enough links, it will be tough to rank for competitive terms in Google. That is definitely the system they have created.
My belief is that the sandbox is definitely an aging filter, but the age required to get out of the sandbox depends on the competitiveness of the keyword(s) being targeted. Add to this that gambling sites are pretty much always mentioned in any “bad neighborhood” discussion on SEO forums, and we might be treated with more prejudice.
For the benefit of others reading this thread, some other things you can try that may help reduce the time in the sandbox is to get listed in DMOZ, register your domain for at least 5 years,buy some one-way links, and maybe try buying a link from the Yahoo directory. Also make sure you aren’t linking out to any Google banned sites. I just found one last night that I had to get rid of. Of course the best way to avoid the sandbox seems to be starting with a domain that is more than 2 years old, if we could all be so lucky to have one of those in this industry.