This becomes particularly important if you want to run a virtual Windows under heavy load or run many virtual machines.
In fact, every Intel Mac runs at least Intel Core, and VT-x very slightly predates Core (you can get P4 parts that have it). It is in fact slightly easier to run a hypervisor on the original Core, and thus the first-gen Macbook, because the Core 2 Duo runs userland in 64 bit mode and the kernel in emulated 32 bit mode, and that's a gross oversimplification made as a small mercy.
In any case, every Macbook sold today --- even the cheapest one --- runs at least Core 2 Duo, which includes not only VT-x but also the advanced I/O stuff Intel did to make TLB flushes not kill performance.
Long story short: you can't buy a Macbook that doesn't do just fine with Parallels or VMWare Fusion.
I was thinking about a 13" white macbook my colleague used to use which I thought had a processor that did not have VT support (as not all Intels do http://www.intel.com/products/processor_number/chart/coreduo...) as there was an issue about it. But, frankly, it sounds like you are probably right and I have made a mistake or am confused (I won't be 100% sure until I can ask him on Monday, and Google is not doing much to help me other than to show how fast HN is being cached - http://www.google.co.uk/search?hl=en&safe=off&sa=X&#... returns this page as the top result minutes after these comments!).
So, good call :)