If you're a regular Skype user then you won't need reminding about the fault towards the end of last week that downed the entire global service.
At the time Skype statements offered woolly info and even an admission that what was happening was "not entirely understood", well, Skype has since investigated the cause of the problems.
It seems that the culprit for the days of problems for the VoIP service was Microsoft's mass patch Tuesday, in which it sent out its Windows Update causing millions of computers to automatically re-boot.
Although just an annoyance for consumers - especially if you didn't save your work before your PC restarts itself - the updates were more problematic on a wider scale. The Skype heartbeat blog states:
"The disruption was triggered by a massive restart of our users’ computers across the globe within a very short timeframe as they re-booted after receiving a routine set of patches through Windows Update."
"The high number of restarts affected Skype’s network resources. This caused a flood of log-in requests, which, combined with the lack of peer-to-peer network resources, prompted a chain reaction that had a critical impact."
This combined with a software bug meant the result that we all saw - the Skype service, which can usually "self-heal" under these circumstances didn't - leading to as much as two days Skype silence for users.