I would be willing to bet that Amazon do their warehouse and logistics operations on a mainframe too.
NYSE also apparently unplugged their last mainframe in 2008[1]. It appears NASDAQ OMX's INET trading platform is based on x86-64/Linux/Oracle stack on commodity hardware[2]. NASDAQ's US exchange has a record of 194,205 orders per second[3]. The latest VisaNet peak message rate I could find was from 2008 and was 8,442 transactions per second[4]. Based on the fact that Visa aggregates transactions over hundreds of major banks, I would guess that each individual bank processes less credit card transactions. Visa's 2009 volume was 9.0 billion transactions[5]. I couldn't find anything substantial on NASDAQ's stock market order volume, but NASDAQ does about 10 billion contracts/year JUST in US & European option derivatives[6].
[1] http://searchdatacenter.techtarget.com/news/article/0,289142...
[2] http://www.nasdaqomx.com/digitalAssets/66/66992_genium_inet....
[3] http://www.nasdaqomxtrader.com/trader.aspx?id=inet
[4] http://investor.visa.com/phoenix.zhtml?c=215693&p=irol-n...
[5] http://www.creditcards.com/credit-card-news/credit-card-indu...
[6] http://www.nasdaq.com/aspx/company-news-story.aspx?storyid=2...
http://blog.seattletimes.nwsource.com/brierdudley/2008/05/am...
This stark distinction in order of magnitude of scale is why there may be so much incredulity here as to the technical superiority of mainframes.
http://blogs.computerworld.com/14876/london_stock_exchange_d...
2) When was the last time Google or Amazon or NASDAQ or Arca was actually out of service because of hardware failure or maintenance?