This happened very quickly, but when syncing an iOS device yesterday, we noticed that Google safe browsing data was being synced to the device. It's fair to say that, for many, updating iOS devices to iOS 5 was fraught with much annoyance, and when it finally worked, it was easy to not pay close attention to the process. But in the iTunes LCD (the part at the top of the iTunes window that shows the playback timeline and other information), we spotted a message saying "Downloading Safari safe browsing data." This database, provided by Google, is used by mobile Safari to check for known malicious web sites. To check if this is activated on your iOS device, go to Settings > Safari, then look for the Fraud Warning slider. If it's not set to "On," do so; it's a good way to protect your device and yourself from known malicious websites.
We're curious as to how often this database will update - whether it's going to be regularly updated, such as daily or weekly, or whether updates will only come occasionally. If you spot a regularity to these updates, let us know in the comments.
Update: syncing our iOS devices over the past couple of days, it seems that this update occurs once a day, but we have no idea at what time the update is made available.