1. You are somewhat comparing apples to organges here. Google had access to the exact same websites as AltaVista, Excite, and Yahoo, so it's obvious that they c

1. You are somewhat comparing apples to organges here. Google had access to the exact same websites as AltaVista, Excite, and Yahoo, so it's obvious that they could build an alternative search engine using the same data. But if you tried building an alternative email provider, you would not have access to the mails stored at google for training your spam filter. 2. You are contradicting yourself. "When it does become false" implies that it is true at some point, i.e., that there are hurdles to overcome, that is to say, that it is harder for a similar service to exist. Noone says that it is impossible, just that it is harder, and the form that that usually takes is precisely that it takes what you call "dissimilar disruptions" to establish an alternative. Having to come up with a "dissimilar disruptions" obviously is harder that coming up with some small evolutionary improvement.