We're seeing more "gratuitous" sound effects here and there; there's a slightly overwrought chime when you select a clip in the "One Second Everyday" app, and they're all over the Facebook app. Overall I applaud this, as adding to the "juiciness" of sites, and giving immediate, somewhat visceral feedback to user actions.
One thing I don't agree with on the Facebook web version is "caching" notification sound effects until the window is brought to the front - an alert that's not cancelled even if you've read the notification that triggered the sound. I guess it's good to mute notifications if the window is hidden - so if you have multiple FB tabs open, you don't get 3 or 4 little dings in rapid succession. But then playing the pent up ding is weird, as it causes the user to go hunting for a non-existant new event.
On the other hand, Apple is sporting an example of what happens when you don't do enough sound suppression... if you don't disable it, the default is patching incoming cellphone calls to your Mac, your iPad, etc. Suffice it to say, suddenly having 3 different devices blaring at you is not exactly a soothing or top-notch user experience... I feel like they should use some heuristics to only allow one device to do audible notifications in a given proximity.