In all my testing and massive backlinking campaigns, I have never come across any large penalty of any sort.
I see so many people talking about how you can't blast more than a certain number of links at your domains because Google will ban you so on...I think this is ridiculous to be honest.
I think the worst thing Google would ever do is just ignore your site eventually if it is just a bunch of spammy-looking shit and possibly de-index it. But you won't some major ban or penalty.
As far as a "sandbox" goes...from my personal experience, there have been a few times where my sites will "disappear" from the SERPs, but it never lasts long.
In my personal opinion, all the "sandbox" really is basically is Google putting your site on the side for further analysis so to speak because maybe you triggered something that made them want to take a closer look.
In this situation, I never stop what I'm doing. I continue to build links consistently and add good content. This usually works. If I need an extra boost, I also add in some outbound links to quality authority sites.
Just those 3 things is all I have ever needed.
I think a lot of people confuse Google's so-called "dance" with a "sandbox" or penalty, and then stop building links or adding content because of this. This is probably the worst thing you can do.
