Logically, any company that grows too fast is going to have service issues. What does "too fast" mean?
Services that get a lot of press on social media sites (like Digg) often get a ton of new clients rapidly. Call it Flashcrowds 2.0, or the Digg Effect 2.0 --- when a business can't handle the increased load from new clients who heard about them social media and blog sites. Looks like MediaTemple hosting is the latest victim of it. (Flashcrowds on the web are when huge numbers of visitors arrive at a web site in a short time frame.)
They're getting an increasing number of posts from clients complaining about service problems. In several cases, (here and here, for example) the posters who complained and said they would leave have decided to stay on with MediaTemple, but the service problems being documented around the web (scroll down to read the most current posts here) seem to indicate they may have grown far too fast.
The upside for folks searching for hosts is that lots of posters document their experiences, and recommend the best hosts they've found. One that looks good I hadn't heard of before is Deru.