I can play a couple of angles on this one as I have worked with both types of businesses mentioned in this post.

There are those small organizations that have a skeleton crew of IT folks that handle everything from top to bottom. Sometimes this approach yields a savings, but I find the majority of the time it does not. More often than not these types of companies look to their vendors for support of "3rd party" products such as RDBMS's and in many cases Operating Systems. I have seen companies hire on a inexperienced DBA, mostly to save cost, in many situations and management of various areas use him or her as a mat on which to wipe their dirty shoes on. The project goes to hell and the DBA takes the heat.

Large corporations sometimes will just hire someone to fill the position or in some cases just move someone from another area into the position of DBA. The key problem I have experienced with large corps is keeping everyone communicating together. There are so many projects, but so few lines of communication between projects that affect each other. If two systems have to share data via some kind of interface, the teams have to communicate or there will be problems. In these situations I have found DBA's are often getting dumped on and expected to immediately resolve issues without any prior knowledge.

With regard to Agile Development and leaving Development retain full control of the database, this in my mind is like haveing the inmates run the asylum! :w00t: While being agile has its advantages, there are also many disadvantages. When you have a large team of developers all making changes to the Database at the same time you get a bloated, inefficient Database that is chock full of useless Indexes. Simply adding a Database Admin as the keeper of data and Architect of objects and change to meet the business plan will go a long way to heading off major performance issues.

Does this mean that having someone who is designated as the DBA will prevent all types of problems? No. Early on in my DBA career I made mistakes, as many of us do, but that is how you learn.