How can you get so many Backlinks without being penalized?

I have few domains in sandbox because of excessive backlinking... I believe i made more then 30k-50k backlinks on them, all new domains... My sites ranked for good no of time but after some times they disappeared... They are in sandbox from last 6-8 months... Lots of links has been deleted but still some of them got 5k-10k backlinks even though i left work on them few months back...

I had some old domains and i made links with little tweaking in my normal process and they are doing very well......

So in my views excessive backlinking hurts but not for same with every one... Google also have trust value for your site and it will judge after taking consideration of that...

Be careful with "1000+ links in one day" offers. Link building is longterm process which should look natural. It is better to build 30 links every day for 30 days than 1000 links in one day.

As long as you make sure your are getting relevant backlinks, I don't see a problem. If you are spamming 1000s of sites with links that have nothing related to your site, it will bring up a flag. It won't look natural. I am not a believer in quantity. Fewer quality links will be far superior and more effective in the long run than a whole bunch of crap.