The sandbox effect or a site getting banned from google has been in use at google for quite a long time and many websites are still becoming victims. Most webmaster will get to know what Google Sandbox is about once they site has been penalised and when they look for a way out.
Whether deliberately or accidentally, websites can get caught the Google Police Crawler and your site domain goes to a prison. A site can remain in Google’s prison (Sandbox) for around 2 to 4 months. Google’s police crawlers will revisit the site to check the status of the website domain.
If the site webmaster notices that there is an issue and is not showing in google search, and manages to resolve the problem which caused the site to be penalised in the first place, the site reappears within Google. Otherwise your site remains in Google’s Prison for life and you will not be able to get it out, unless you can hack into Google’s database to modify your site details ot get in touch with Google and justify you have done nothing wrong.
Most webmasters ignore Google Police Crawler’s and later find that it is too late when their site is sent to the sandbox. If you find any problems with your site’s google rankings, it could be possible that your site is entering the Google sandbox.
Google has a rule which changes every 2 to 3 months and sites which do not keep their sites updated with the changes in Google’s algorithm, your site is slowly removed from Google. It’s like a slow poison where your site will die slowly without you knowing because google will never notify you or disclose openly that your site has been penalized.
In the past sites when sites were penalized, they were immediately removed from Google. In most cases today, your site will be penalised slow and removed from Google or you may lose your page rank and your site no longer will rank as it did before.
Always check which sites you are linking to, as linking to a bad site or neighbour can cause penalties. If a site your linking to has been penalised by Google your site may also be penalised. For example, if you were to allow a criminal on the run to live at your house, you would also be punished when caught.
Hope this helps