The concept behind heatsinks is that they get rid of heat quickly through convection through the air because of their large surface area. They don't hold heat. If the heatsink was warmer than the CPU, the CPU wouldn't transfer any heat to it.
In response to my:
"Heat-sinks (hunk of metal only) passively cool.
All they do is absorb heat from the CPU and let it dissipate into the case. Because they rely on fans up to 10 inches away, they tend to be much larger to hold more heat. If you search for 'Dell heat sink' on Ebay, you;ll get a feel for just how large they are. (For example, the one in this link is about 6-7 inches tall and *heavy*: http://cgi.ebay.com/Dell-Dimension-C...ayphotohosting)"
I never claimed they got warmer than the CPU. They, do however hold the heat from the CPU and allow it to dissipate into the surrounding area, as I thought I pretty much mentioned. You're partial-quote of my Post is a bit misleading, no offense, but did you read the entire Post and see "Because they have more bang-for-the-buck cooling power, they are small compared to versions without fans" in the next paragraph describing HSFs?
The real reason heatsinks that were intended to be passive are so large is a little different, too. If you took a very large HSF like the Zalman 9700 and ripped the fan out of it, it'd be ineffective as a passive heatsink.
Passive heatsinks have a larger area between the "fins." This allows air to pass through the fins and pick up heat without being forced through by a fan. The Scythe ninja has almost a centimeter between each layer of fins.
Again, apples to oranges. Heat-sinks are designed differently from HSFs. If you take a large HSF and rip the fan off of it, of course it will under-perform because that's
not how it was designed to work. Comparing the two is like comparing a Celeron from 8 years ago to a new 45nm C2D; yes, they're both CPU's, but other than that, nothing in common.