1. Google Buzz will integrate very nicely with mobile phones and maps. So this will further impact mobile social networking and online communities on the go. This could affect events PR and marketing quickly
2. It will be easy to use (where many say Twitter isn't). Google Buzz has already been described as something so simple 'your mother' would use it, according to one watcher I'm following
3. Search engines will find content much more easily than with content on Twitter. For brands this is a reputation management issue
4. For PR people, the address book has always been valuable. Whatever your current email address book is, exporting it into Gmail as well will create an instant social network
5. There will be an 'enterprise' version of Google Buzz coming soon. This will change the way internal communications works as well (and might thwn also create the Yammer.com killer)