no criticism or i will hunt you down...?

I don't think there's any definite answer to that question. However, the fact that Marcello died in his early 50s should give us pause to think. People died early in those days, it is true, but their biographers usually tell us about the accident or disease that brought them down (in the case of Mozart, for instance, his death was preceded by symptoms that modern day doctors put down to a fatal kidney ailment...).

In the case of Marcello, nothing. Apparently he just wasted away. Which, I think, you should combine with the fact that he had to leave Istria where he had a financially comfortable position because "the climate affected his health". Without stretching the evidence too far I think we can assume that this weakening of his health was what ended his life in Brescia in 1739. Which being so, I'd venture a guess and say: tuberculosis. ("Consumption" in the language of those days.) This is precisely the kind of illness people got from bad weather (and bad food and too much booze...) in those days, and the kind of illness that would follow you even as you moved unto warmer climates and in the end bring you down. But, again, it is merely my guess.

that is SOOOOOOOOO funny. Gotta tell my best friend that one. but seriously, I would go to the net until I get my answer. Put that question in the address bar and see what you get. You can also go to a sight called www.ask.com Formerly ask jeeves. But just type your question into the address bar

Sorry, searched a lot but found nothing, may be it was because of 'Natural Causes'

I think it was a fever, or maybe pneumonia, I'm not 100% sure

see http://en.wikipedia.org/wiki/Benedetto_Marcello

Good Luck!!!