Folks saw congestion from a massive free content drop this past week. But as folks had called out, that was the CDN angle of distributing that content rather than the actual game play. There is a rather long discussion about that in the "akamai yesterday - what in the world was that" thread from Jan/Feb/March. Whether people end up adjusting plans around large content distribution at this time, I guess remains to be seen.
(*this is 100% my personal opinion**) Perhaps we are approaching at time when large content distribution events such as the one noted above will be configured so as to minimize any potential network effects (e.g. pushing to off-peak or applying server-side per connection rate limits). The Internet is a shared resource and as such we all share responsibility to work together and act in a way as to maintain the performance & reliability of the Internet as a whole. JL