My experience so far:
I haven't been hit directly with it myself - but several friends and one of two bots I have running on a sim got whisked away.
It appears the greifer attack is limited to a number of meters (from where it is deployed) as other people in skyboxes and the far parts of the sim were unaffected the whole time. This may indicate the attack may be limted to the attacking viewer's view range or an object detection range.
As for the bot - according to the logs she was hit with an object masking her own name, ripped off her base station and got sent to several sims including the cornfield and a weapons sandbox a couple of times and ended up finding her in a pile of other unfortunate bots from other sims in one of the Brony places. Had to relog the bot to send her home.