First, my apologies though to the decent people on this newsgroup (and
you know who you are)...

Answer #1:
None you blankety-blank-stupid homeowner - they don't screw lightbulbs
-- they just screw customers...

Answer #2:
TEN
1 to berate the customer about how dangerous it is to change a
lightbulb since there is electricity inside the socket and he could
burn down the house or maybe even the whole neighborhood
1 to tell the homeowner how unqualified he is to even attempt to do so
1 to brag about all the certification, training, and years of
experience they have in light-bulb changing
1 to just berate the customer and curse at him for even asking a
question
1 to assume that since the customer is asking a question, he must be
"cheap"
1 to talk about how already by Wednesday night they have put in
more than 40 hours of light-bulb changing so they don't have time
to help anybody.
1 to tell the customer that he shouldn't even be asking any questions
but should immediately call a repair tech anytime a light bulb
burns out
1 to say that not only is a tech needed for changing
a lightbulb but that legally homeowners should be calling a tech
each time they decide to turn on and off the light bulb
1 to warn how no light-bulb changing technician would ever want
to work for the diy'er since he is such a fill in the blank insult
1 to spout useless, irrelevant (and wrong) pseudo-technical
misinformation about how to fix a doorbell

So you say but these 10 alt.hvac "pros" still haven't actually changed
the lightbulb -- no problem. The homeowner just changes it himself
since you really don't need an arrogant, trailer-trash alt.hvac tech
to change a light bulb!