When to use a blowoff tube

For dark beers or beers with a specific gravity greater than 1.060, in my experience, a blow off tube is need to keep from having an overflowing mess.

Here is a picture of a porter that is only 24 hours into fermentation. You can see the amount of gunk on the glass in the head space got up to the airlock. I pitched two cups of slurry from a previous batch of English Pub Bitter and the fermentation took off like a rocket. In five hours the tube was making a tapping noise every couple seconds as it bubbled. The strain is White Labs British Ale Yeast.