Simple storage
Simple messaging
These types of services are great for decreasing development time and makes things easier to manage for larger scaled sites. The problem is reliability and backup.
Amazon may have 99.99 % on their network, sadly when running a site with millions of users you notice when a certain geographic area or network can not access your web site. This happened due to every network does not have many routes and many providers. Saying this amazon could easily become inaccessible by the server causing down time. Add that on to regular downtime caused by random events and your site is starting to look unreliable.
Worse case I seen for Internet failure is providers in the financial district after Sept 11 Terror attacks. With the power out and the servers hot every thing cooked at a nice 120 F.
Of course everyone promises that they are going to be 99.99 % there, what happens if you are that 0.01 % and all your data is lost ? Once again with large sites this WILL happen at one point or another. Therefor you have to have backups.
Worse case I have seen for backups is having a data center destroyed. I had the customer setup with three backup systems in place. Two where on site and the third was remote site. Only the remote backup server was active, in a 24 hour period the customer went from four copies of their data to one.
On the flip side, these services do make things faster to develop and if you do have a backup of what is on amazon you are all set tell you need to move in house. For many sites this will never be needed.
