I'm just brainstorming here, but here's an idea to give this some context for Blogger. Blogger goes through your profile, blog, or each post. Based on your specifics (name, geography, specifics), as well as blog and post content. You can select some as defaults, and select or deselect which ones you want. I invision the interface being accessed by an icon on the toolbar inside of Google, and pulling up a "suggested tags" tab, in addition to a profile tab as well as a blog tab.