I just did an electrical job where I spliced in about 2' of 'normal'
gauge elec. wire (#14?) in a long run of heavier elec. wire (#10?).
Everything seems to be working fine, but I wonder whether mixing the
different gauges of wire poses any fire risk. Anyone have any thoughts
on that?

This does pose a fire risk and it is not to code.  If the previous wire
was #10 then this most likely allowed for a higher rated circuit
breaker.  By putting a smaller gauge wire on that line, that section of
wire could have more current passing through that portion of the wire
then the #14 is rated for without tripping the circuit breaker.  This
is where the risk of fire exists.  I'm not certain of your exact
application, but I would seriously suggest, not using the circuit until
this can be corrected.

You make me wonder if this is a joke.  Assuming it is not, I totally
agree with the other poster.  Your electric stove would be a fine
example of putting more current through a wire than is electrically
safe.  In the case of the electric stove, the burners are designed to
"over heat."  A 14 guage wire is designed for a maximum of 15 amps.  A
number 10 wire is what you would use on your electric dryer, up to 30
amps.  That two foot section of 14 wire will, if current demand is up,
glow just like that electric stove, or the filament in an electric
light.

The electric "code" spoken of is always in the interest of safety.  I
can understand that sometimes code is a pain in the you know what, but
it is there to protect the people who use the electricity.  

Last point:  If, I repeat IF, you were to find that the breaker at the
other end of this number 10 wire was in fact a 15 amp breaker, then your
splice would not be a problem.  You can use larger diameter wire (lower
guage number) but not the opposite.

You have a dangerous situation.  Fix it NOW!

-30-
Shel