Entries disappeared, auto_increment also reversed, web app security vulnerability or DB Error?
If you are using external DB Hosting, you should expect some intermittency due to the hosting. There are no native MySQL mechanisms in play. I have seen happen while evaluating XEROUND.
When I signed up for the 30-day trial, I was given two public IPs to access the MySQL Database. I loaded a lot of data on it. I was able to access it from one East-coast based public IP and the data was not immediately manifested from the West-coast based public IP till minutes later.
You have find out from Mediatemple if you can look into using their Reboot and Repair Utilities. You may also need to make sure data is being coalesced fast enough for snapsots to be reasonably replicated.
There is one major concern. Under the FAQ section I just saw something very, very disturbing for Mediatemple's Grid Hosting:

Which versions of LAMP software comes with my (gs)? The (gs)
Grid-Service currently features the following versions of software:
PHP 5 (click for specific version)
Perl v5.8.4
Python v2.4.4
Apache 2.0.54
MySQL 5.1.26

I really hope that is a misprint. Why?
The first GA release of MySQL 5.1 is 5.1.30. Mediatemple is offering MySQL 5.1.26.
Why on God's green earth would someone offer a Pre-GA version of MySQL 5.1?
Please, make sure you are using MySQL 5.5.21 (or 5.1.61 if you have to have MySQL 5.1)
UPDATE 2012-03-05 22:51 EST
You should setup MySQL Replication is addition as a secondary form of redundancy to an outside hosting service (such as Amazon EC2) for a while. That way, any missing rows should at the very least show up in the binary logs on the Master and the relay logs on the Slave.
If your data is missing in MediaTemplate but is present and accounted for on the Slave, I would consider switching out of MediaTemplate Grid Services. If it happens more than once, switch out immediately.
If the data on the Slave is exactly the same, you can rule out Database Replication at all levels. From here it is time for a deep dive into WordPress configuration. You can also look through the binary logs to see the data you had was once there at one point disappears at another point.