How To Add Top Link Bar Inheritance Using PowerShell for SharePoint 2010

To Add Top Link Bar Inheritance, open up the SharePoint 2010 Management Shell and perform the following:

For one site:

$web = Get-SPWeb -Identity http://portal.company.com
$web.Navigation.UseShared = $true

For every site in the Site Collection:

Get-SPSite -Identity http://portal.company.com | Get-SPWeb -Limit All | %{$_.Navigation.UseShared=$true}

You Are Done.