In a video interview with Digg Dialogg, she said that "certainly there are things we've learnt from that, certain things we would have done differently" with Wave, which is being shut down at the end of the year.
The closing of DejaNews, a site for Usenet discussions, wasn't handled well according to Mayer. "Shutting down Dejanews.com at 11am on a Monday morning, and not having anywhere to post to or browse usegroups was perhaps a mistake," she said, referring to the day in 2001 when Google acquired the archives, moved them and renamed them as Google Groups without warning.
The final error Mayer regrets is "launching Gmail on April Fools day," which she said was "widely misinterpreted." Considering Google has a pretty hilarious history of April Fool's pranks, it was believed that it was just an elaborate joke when the search engine launched the invite-only email service in 2004. [Digg Dialogg via The Next Web]
UPDATE: Of course, Mayer may've skipped past the Wi-Fi snooping and Buzz issues because of the ongoing legal cases involving the two services. Labeling them as "mistakes" would've caused an uproar.