I have also also had the oom-killer kill my freeswitch. Trouble is by the time I get to the system, the problem has gone away, and I can restart freeswitch without any problems.

On the last occasion I was getting flooded with incoming SIP REGISTER packets, so I suspect that may have been the culprit at least this last time (see archives). 

(Not absolutely convinced this was an attack, it seem to stop immediately after I restarted freeswitch, so maybe somebodies mis-configured system was trying desperately to get a response, which wasn't going to happen while freeswitch was dead? Still seems strange though that somebody would be trying to contact my server...)

Haven't had any recent problems.