Although the subject is interesting the page, published on 16th March 2010, is poorly researched blog-spam. It is essentially just copied from one of the numerous pages that say the same thing, such as this one published on 27th January 2009
According to one of the linked articles, they are suspected to be hitchhiking in the ballast of large ships, so their habitat is unnaturally expanding. There could always be other factors too, like an over-fished predator.
Lots of animals can do that, although the ones that can survive in a body—for example, tapeworms—usually start preferring to survive in that body (it relieves you of all the work of creating a biological equilibrium of your own), so they evolve to hold on inside instead of coming out.
They are jellyfish, and jellyfish thrive on the recent development that is large amounts of nitrates in the oceans. Think greenhouse gases, but instead of heat in the atmosphere, it's algae and jellyfish in oceans.
Overfishing is the culprit here. With less fish in the seas jellyfish - immortal and regular - can procreate much more easily, and have access to more food. Here's a relevant article: http://www.digitaljournal.com/article/273850
I am surprised the tourism lobbies are not fighting the fishing lobbies on that one.
Good observation. A spike in population implies a recent change in the organism or its environment. Since most multicellular organisms cannot evolve that quickly, it's more likely that there was a change in the environment which this organism was able to take advantage of. I doubt that their numbers are spiking because "they are bale to bypass death".
Did they like ... just evolve or something? You'd think they'd have spiked before now and reached equilibrium.