As doktorhonig said. And this behavior is there since google bought it. It has some cons and some pros. If you have problems or for whatever reason you want to load whole video first, simply mute it and play it. After a while return and play again
I really have no choice in the matter since the best connection where I live goes up to 2 mbps. So often I can't load videos as fast as they play. I did think before about the very same thing you're suggesting now. This doesn't work however because, like I stated, YouTube unloads all footage you've just played. So you can't just go back and rewatch the video whole.
Or if you're using Firefox, download it using for instance the DownloadHelper extension and watch it offline.
I will check this out. Thanks.
*sigh* So this is the sin of living in the age of fast internet. Companies expect everyone to have 10 mbps connections. I never really cared about not being able to download gigabyte files in under a minute, let alone stream them. I just wish companies wouldn't make their websites impractical to use for anyone who doesn't live in a large city center.