Bling is a feature built into some attachments that allow them to shine brilliantly on a timed basis. It uses particles. Bling is considered by some to be a significant source of client lag, especially when a large group of avatars is one area, and many of them are wearing scripted objects. See also blingtard.
Since particles are rendered only on the client side, for bling to create server lag there needs to be repeated calls to the Particle System to create server lag. Many find the use of bling to be aesthetically displeasing.
(See also Poofing)