Instead of removing links in vtiger's database, hack with Smarty templates, etc. We have created a simple extension module to avoid doing the same task over and over.
Once installed, this vtiger module will automatically hide the Vtiger Extension Banner from your CRM dashboard. You can still enable the banner is choose so by clicking the down arrow in your home dashboard.
More information and documentation: http://www.vgsglobal.com/blog/vtiger-hide-banners-dashboard-module