I am still on the "fence" with DE....

I am not finding anything useful in the way of studies to recommend it here. I will at this time not be using it myself.

I did find a person reporting that it caused rectal bleeding. So if anyone here notices this side effect, that is a sign to stop using it.

I would wear a mask while measuring it out. I do not think it is safe to inhale.

I would also suggest to take "vacations" from using it, in case it is mined from a toxic source. In the past several popular "natural" products have been found to be contaminated with heavy metals. Blue green algae with fluoride, Coral Calcium, and dolomite. These were sold for YEARS to the public contaminated.

I am finding people on the net who recommend taking probiotics with DE. The reasoning for this is that DE is purported to kill organisms in the GI tract, and this would be nonselective and include beneficial organisms we depend on.
For example, one organism is responsible for removing oxalate from the veggies we consume. Then this oxalate is absorbed and excreted by the kidneys, which can develop into oxalate kidney stones.
http://www.ncbi.nlm.nih.gov/pubmed/20602988
If over time these beneficial organisms die off, then they need to be replenished.
Antibiotics will kill off these beneficial bacteria too.

What I see online so far is a "fad". This may turn out to be very useful, but the human oral consumption of DE still remains to be examined more carefully IMO.
The FDA so far has this on the GRAS list (generally regarded as safe). But if you examine the GRAS list you'll find some scarey things. So I wouldn't rely on this classification as an FDA endorsement. Some DE is consumed every day by people, as DE is used in food production. We just don't have figures easily found to describe "how much" we eat daily.