http://blog.us.playstation.com/2009/04/01/ps3-firmware-v270-update/ (Walkthrough video included).
If I remember correctly, the XMB messaging system is used for exchanging LBP level objects. So the attachment file size increase can be useful.
EDIT: Also a browser plugin enhancement: http://www.webwire.com/ViewPressRel.asp?aId=91035
In addition to Text Chat, we’ve added a few more enhancements:
Friends list on the XMB (XrossMediaBar)
Sort your friends via their online status
Attach larger files to the messages you send to your friends (file size will increase from 1MB to 3MB)
Video delivery service on PlayStation Store
Video files you’ve purchased from the PlayStation Store can be backed up to an external storage device and then restored to PS3’s internal hard drive for playback – so you can clear up space on your hard drive and then restore the video anytime in the future
Videos you’ve purchased for PSP (PlayStation Portable) system can now be transferred to PS3 for playback
If I remember correctly, the XMB messaging system is used for exchanging LBP level objects. So the attachment file size increase can be useful.
EDIT: Also a browser plugin enhancement: http://www.webwire.com/ViewPressRel.asp?aId=91035