Don't be too worried, RG
The 16-core score is from a (still current, but) older generation Intel processor codenamed Tulsa based on the Netburst architecture, whereas the 4- and 8-core results are both based on the newer Core microarchitecture. On that basis, you wouldn't expect to see linear scalability per core.
Tigerton will hit the streets next quarter - the Core microarchitecture replacement of Tulsa - then you can do a more realistic "scalability per core" test.
Intel soon switches to a 45nm fab process - boosting performance and lowering power consumption across the range. Then there's the successor to the Core microarchitecture just around that corner...I think Intel is giving IBM a pretty good run for its money.