Wasn’t watching steam when this assert + crash took place, all I can give is crashids.

userfriends.cpp (1457) : Assertion Failed: steamID.BIndividualAccount()
Assert( Assertion Failed: steamID.BIndividualAccount() ):/home/buildbot/buildslave_steam/steam_rel_client_ubuntu12_linux/build/src/clientdll/userfriends.cpp:1457

Installing breakpad exception handler for appid(steam)/version(1360621458_client)
Uploading dump (in-process) [proxy '']
/tmp/dumps/assert_20130212145858_1.dmp
success = yes
response:  CrashID=bp-698974f4-7847-4085-8dfa-d8a6b2130212
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
Assert( Assertion Failed: m_cAPIPipePending == 0 ):/home/buildbot/buildslave_steam/steam_rel_client_ubuntu12_linux/build/src/clientdll/../common/pipes.cpp:676

Installing breakpad exception handler for appid(steam)/version(1360621458_client)
Uploading dump (in-process) [proxy '']
/tmp/dumps/assert_20130212150215_2.dmp
success = yes
response:  CrashID=bp-94472ccb-2236-45b8-b847-bf1a82130212
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
pipes.cpp (676) : Assertion Failed: m_cAPIPipePending == 0
Uploading dump (in-process) [proxy '']
/tmp/dumps/crash_20130212150535_3.dmp
success = yes
response:  CrashID=bp-0445ffae-0c46-4264-b6f7-61dcd2130212
/home/john/Steam/steam.sh: line 561: 14389 Segmentation fault      (core dumped) $STEAM_DEBUGGER "$STEAMROOT/$PLATFORM/$STEAMEXE" "$@"

Sysinfo, https://gist.github.com/johndrinkwater/4721913