Is there a name for these long, snaky paint drips?

If you accidentally repaint a car too quickly, without proper flash times, huge paint sags and runs can flow down and ruin the finish, especially on vertical panels.

(thefreedictionary.com)
sag noun 2a. A sagging or drooping part or area: tried to brush out the paint sags.

They're also often called paint runs.

In the graffiti culture they are just called drips, and are often used intentionally for artistic effect.

Drips - At first drips are the sign of a novice painter who does not have good can control. Over time a writer can get so good that he or she intentionally drips their tags in order to show style....This style originated early on in New York subway graffiti with home made markers (here)

Yesterday, a newcomer named Pen posted the following answer:

We grew up calling them 'holidays'.

The answer has since been deleted. It seemed an odd answer, but it didn't sound offensive or gratuitous to me. So, I looked online and found the following definitions:

Painting and Coatings Terms and Definitions

Holidays: Application defect whereby small areas are left uncoated. Synonyms: Misses, Skips, Voids, Discontinuities, Vacations.

and from Coating Defects-Common Coating Failures and Causes

• Coating Defects: Runs, Sags, Curtains, Wrinkles
  Runs, sags, curtains, or wrinkles may be caused or worsened by: applying the coating too thickly, using too much thinner or using the wrong thinner, surface too hot to apply the coating, applying a coating at the end of its pot life, wrong thixotrope used in manufacturing , improper spray technique.

• Discontinuities: Skips, Holidays, and Missed Areas
  These defects are exposed areas of the substrate or previous coating, caused by poor application technique, lack of stripe coating, and/or lack of or poor inspection. Quick recognition and repair means the repair is easier and it will blend in better.

If the drips or ‘sags’ are large then the term curtains, used in the painting industry, is also appropriate.

Curtains
Large sagging or runs of paint due to improper application.