If we are talking about 30 years from now, I would never say never. I could be wrong fo course, but I could also be right. There are many ways the biocomputer can be implemented but moods and such are not part of the picture. Generally it just involves DNA molecules and their properties. So it is not like a brain and it is not sentient. One of the major concerns though is that should some of these DNA strands leak into the environment they could potentially be a deadly virus. So I guess each machine would be a biohazard.
But 30 years from now we would likely have network connections at such speed that all processing bar simple processing would be done remotely.
ah, you were talking about a DNA based chemical computer rather then a brain in a jar living organism computer.
The notion that a DNA leaking into the environment becomes a virus is poppycock. Viruses are protein capsules which dock with a VERY specific cell type to inject it with its DNA (or RNA) which is very specific genetic code which uses the host cell's genetic machinery to replicate itself. DNA "escaping" from a test tube is not a virus, it has no specialized protein shell with cell recognition receptors, it has no injection mechanism, nor does the DNA itself has any "take over cell and replicate" code in it.
I don't know who told you this is a major concern, but whomever that was knows absolutely nothing about biology. Loose DNA is totally harmless. In fact it is perfectly safe to eat... Everything you eat, with the exception of milk, most of an egg (there is some DNA in it, it has 1 single cell), and honey, is a living organism (yogurt is living bacteria, mushroom are living fungi, fruit/veggies are living plants, and meat is living animals). Each and every one of their cells has DNA in it, which your body digests. And have you heard of ATP? the "energy molecule" used in cells in your body? well, actually there are four of them. ATP, GTP, TTP, CTP. DNA is made out of 4 molecules, their names are shortened to A, T, G, C... Notice a pattern? TP just stands for Tri-Phosphate, and the various molecules that make up your DNA also carry energy for the cell... here is more info:
http://en.wikipedia.org/wiki/Nucleoside_triphosphate
Although, everything in excess is bad for you... I wonder how much DNA at once would you need to consume for it to be harmful...
Anyways, while the DNA computer is a very different issue than a brain in a jar computer, it is still vastly impractical. We are not in any sense close to figuring out a way to even make it practical (assuming its possible to do so). My educated guess is that it is not possible to make it into a practical alternative (in terms of price, size, and performance) to an electricity based computer. But unlike the other design type, I am not certain that this is actually impossible.
PS. On some things you can say never.