Wait, isn't "Memory Clean" just one of those apps that allocates a huge chunk of memory, forcing the OS to page everything else to disk? Those things are snake oil, they don't improve anything and in fact are often worse than doing nothing at all...
I think this panic started with Windows Vista where there was no distinction between actually used memory and memory used for caches and buffers. Hence the complaints about how Vista was so inefficient, it didn't have enough memory even when freshly launched with no apps open.