What's the downside of using backup and restore site collection as deployment methods in SharePoint2010?
The downsides are:
- an not restore a previous version of SP site backup to a new version of SharePoint environment.
Depends on your development process, and the purpose of the site collection. For situations where the site is developed in a dev or staging environment, and then moved to a production environment, there isn't really anything wrong with the backup/restore method for the initial deployment.
The downside comes when you need to decide how to maintain the site, and this comes down to how the site is being used. For an information only site such as a publishing site, where end users or content editors are restricted from making changes to the production version, it might be ok to continue development in one environment and use backup/restore to deploy changes to production. However as soon as the production site can be modified by end users, you're in trouble because you don't want to risk losing data by overwriting the real site with a dev version.
Here are some of my thoughts off the top of my head: