Right. Google is successful because it was the last search engine. It provided a completely novel way to do search (links vs. keywords) and Facebook will be valuable if it turns out to be the last social network. However, to be the LAST MOVER you have to provide a value at some arbitrary, but huge, number. Let's say a 10x improvement over the incumbant (or various substitute products). That is why email is difficult to dethrone. It works well, is relatively secure (you can sort of choose your level of security) and spam settings make it reasonably painless. So this app is going to have to be a much better experience than hangouts (probably easy, hangouts is shit), or whatsapp, or email, or a phonecall, or instagram etc. This can be done, but the execution has to be perfect, the value proposition has to be 10x better than the one or two substitute services it replaces (largely phone & messaging) and it has to have a growth pattern that is substantial enough that it can be reasonably assumed that at least 80% of my contacts are using it.

so to be last mover here they probably need

>a product that is 10x better than a combo(or stand alone instance) of SMS/messaging apps/email/facetime/phone etc

>widespread user adoption

>trust/security

>a revenue stream

It seems cool, but it is a tough space to dominate.