If Skype "kills" SIP, it won't be because of anything Skype did particularly well (IMHO). It will be because only Skype seems to get free adverstising from any and every commentator.

It seems that the dozens of standards-based VoIP operators almost never get mentioned by name (although they often get acknowledged as a group), despite their millions of collective users and their increased flexibility in how the applications get used. Naming only one or two seems unfair, so only the proprietary S-word gets cited at all. Or, occasionally, some commentator will try to complain about this or that perceived failure of one of the standards-based operators.