awk/sed output from system_profiler on 10.6.8
Use this sed instead:

|sed '$!N;s/\n/ /' 


system_profiler SPMemoryDataType | awk '/Type/ {print $2} /Speed/ {print $2}'|sed '$!N;s/\n/ /'

output:

DDR3 1066
DDR3 1066
DDR3 1066
Empty Empty