Ping di un blog vs Submission di un sito

Not too long ago, bout 2 years I guess, there were a couple of blog search engines in the works. These engines were bootstrapped so saving money was of the utmost importance. They wanted to track blogs in real-time but knew that wasn't possible because they didn't have the number of servers required to do it, even back then. On top of that they didn't have the bandwidth to do it either because all of that requires loads of capital. So instead they decided to make it easy for those who owned blogs to notify them when their blog had been updated. This is what the blogosphere typically means when the word ping is used.</p>

Jason Dowdell

Qual è la differenza tra una submission di un sito in un motore di ricerca ed un ping per un blog?
Perché questa differenza?

Entrambe le domande sono risposte da Jason Dowdell nell'intervento di cui riporto sopra uno dei passaggi a mio avviso più interessanti.
Un ottimo articolo scritto in termini semplici e comprensibili anche dai newbie.