Using multiple power outlets safely.
FIRST - Obey the manufacturers instructions!
Introduction
I was prompted to put this together after hearing a news item about a fatal house fire in Adelaide, South Australia, then another fire at an unoccupied house in Paringa, S.A. Both fires were attributed to multiple power outlets. The Adelaide fire officer who reported on the fire seemed a little puzzled as to how the Adelaide fire started. It certainly was caused by the multiple outlet, but he stated that it did not appear to be overloaded. The Paringa fire was reported to be caused by the outlet, although the computer equipment that it was used for was was not switched on. There was a lot of discussion about the official cause report, and bunched wires causing a heat build up. You can measure the heat build up yourself, with predictable results. Even with plugpacks contributing to the heat.
My Experiences
I have had three bad events from multiple power outlets, the first actually
igniting paper nearby, leaving ashes on the floor. The remaining ones
suffered burning, melting, and blackening on the top, and holes melted through
the plastic at the bottom. At all times, they were only powering electronic
equipment, and were nowhere near their load capacity. So I first assumed it
was a manufacturing fault which took a long time to cause problems. But I
had to reconsider this theory after the further melt-downs. Unfortunately,
I threw the first one away. Here are the last two which occured over the past
12 months.
The first two were a mystery, then I found what was happening. It was quite
a surprise, and because of the time delay involved, quite confusing.
The last occurrance commenced with faint hissing or crackling sounds in the
room which were hard to locate. Occasionally, there was a mild "pop"
sound. After much waiting and listening, I found it was coming from a multi-block.
But this time the evidence was still there!!! 
The
male dog had done his thing on it. We have always had a dog.
The tricky part is that it is not an immediate cause of problems, it can take
a long time for the urine to get to where it is harmfull and cause heat build-up
although the current involved is low.
It doesn't blow a fuse, but might cause a safety switch to break, depending
on whether the leakage (?) is to earth, or neutral. In our case, it was 12-24
hours before anything was noticed to be amiss. 
As
I said, I was puzzled by the first occurrances, as the heat that developed
had evaporated the cause.
It would be interesting to know if any of the past fire victims had dogs.
Maybe cats, possums, rats, or mice could be involved too.
We now keep multiple power outlets off the floor to avoid
repetition, and screw them to the wall if possible to keep them away from
the dogs.
I have emailed MFS, SES and our local newspaper of my experiences, but have
received no response from any as yet.
I don't know if I have a credibility problem, but as you can
see, it DID happen! And enough heat can be present to ignite anything burnable
nearby.
So use this info as you will, and at least cover your multi-blocks if you have pets.
This is the menace who caused the last 2 problems!
UPDATE!
Has a manufacturer caught on??!!
I saw this type of socket and originally thought that recessing
it was asking for trouble......then I noticed the two indents.
Could it be that they are intended as reservoirs to catch any limited liquid
spills?
In the situations I am talking about, they may well assist in keeping liquid
away from the active and neutral holes.
Your comments welcome!