I was doing some research for tools to make list configuration across multiple sites easier and came across this bit of information about site collection backups:
You should lock the site collection first, then do the backup, then unlock the site. You do this by using the setsitelock stsadm command to lock and unlock the site, and getsitelock stsadm command to inspect the lock state. It’s all detailed here at http://technet.microsoft.com/en-us/library/cc262811.aspx , which I just came across after reading the last sentence of the home page for Keith Richie’s SPLSBackup utility on CodePlex. (http://www.codeplex.com/splsbackup ). Keith wrote a number of 2003 and 2007 utilities when he worked for Microsoft, and now he’s working for another company doing more SharePoint utility development.