http://www.pcworld.com/article/160153/google.html
http://news.softpedia.com/news/Longest-Gmail-Meltdown-in-His...
http://arstechnica.com/information-technology/2012/12/why-gm...
http://www.computerworld.com/article/2486914/web-apps/update...
Keep in mind, when comparing it to your experience, is that not all customers are necessarily down when there's a problem.
I'm not dumping on Gmail, running a giant system like that has got to be extremely challenging to get right.
But let's not wear rose-tinted glasses about the cloud. It can be great, but for some applications you can get better reliability by competent people deploying reliable software on reliable hardware.
This doesn't jive with the tech industry hype train though, hence, it being "myopic" to consider running your own services internally.
Is there a list of outages on other 'major' services of this magnitude?
The general trend I follow is that you're good at things you do regularly. That means that internal systems tend to be much worse at recovering from failure (i.e. the time to recover can be days or even weeks) unless they are careful to design with redundancy in mind and practice it regularly. That's a time-honored tradition in large IT shops but it's also one which often requires constant effort to justify the "wasteful" expense even in places which should know better.
Case in point: It's informative that you refer to "mail servers". The plural makes it clear that the company in question isn't in the same league, size-wise, as the target market for most SaaS vendors.
Typical companies, though, are mostly Windows shops and really are looking to get something more along the lines of an integrated communication/collaboration/scheduling tool like Microsoft Exchange or GMail.
This is exactly it. Even if not intentionally designed, it ends up that way. As andrewstuart2 mentioned above, "[customers] also got the full expertise of the salesforce engineering organization (which clearly is far from incompetent) being brought to bear on the problem, at no extra charge to them as a customer". This is great I guess, but if your home-grown solution doesn't use, say, Oracle, to start out with, you're going to eliminate a heck of a lot of necessary engineering expertise when things go wrong. Break up systems even more and suddenly just one generalist can do it all on the side...
Cloud services just have to be equal to internally run ones in this regard, since they save so much in other areas. So I guess people have to decide: is 20 hours of downtime every few years worth running your own services internally and paying people full time to manage them?