Network rate limiting?
In some testing (from a 100Mbps NY client) the best I've been able to achieve from any of my Linodes in Newark is around 40-45Mbps in aggregate (singe or multiple streams) for a static file served by nginx. I even seem to get about that rate between two of those Linodes over the private network.
By comparison, downloading the 100MB-newark.bin file from newark1.linode.com yields 80-90Mbps (likely my client connection limit).
I thought maybe it was xen/virtualization overhead, but I can download the 100MB-newark.bin file to a Newark Linode at 500+Mbps, so it seems some other limiting is going on.
I once tried downloading someone else's (not Linode-hosted) 100MB test file from my 360, and got almost 500Mbps (60MB/s). Seriously, it took less than 2 seconds. That looked crazy… Maybe the file was gzipped by the server or something, but I didn't think to check at the time. Maybe incoming bandwidth isn't capped?