Must Yahoo regret not taking over Google's rank system?
Google's rank system itself is nothing, especially in the standpoint of intellectual property. The success of Google was thanks to other supplementary technologies, good environments, and subsequent good managements: supports by Stanfordians, supports by US government, Silicon valley's desires to overcome Microsoft, USA people's desires to replace Yahoo rooted by a Chinese. Wall street Fund's desires, bold reinvestment by Google's executives, etc.
Likewise, Android would have been nothing if it had not met Google. The success of Android was possible since it's Google in USA environments. If Samsung had taken over android, it would have been a big failure. What could Samsung as a manufacturer do in Korean environment with poor software infrastructures?
Meanwhile, Flexible Double Entry Bookkeeping System and B16x2 Keyboard shall remain splendid forever in human history. The one grasping one of them shall be one of the last winners.