Incidentally most people put more enough information on Facebook for a very effective hex to be cast against them... I wonder how many of them also have shielding in place to minimise abuse of that information... Great resource of info for witches - Facebook!
I personally believe that a spell has the most potency when worked by the person who wants the results. When I'm asked for spells I usually help construct the working but I'll often leave the actual casting down to the person themselves. I'm not of the opinion that magic is something highly specialised that only experienced witches can perform, I actually think most people could manage a pretty credible attempt at spell work. It's lack of belief in magic not lack of ability that turns so many people away from it.
I do perform spells for those I know personally - both by request and to improve people for my own ends (!) Generally I cast for people I know and against those I don't. The against spells refer to some of the animal and child cruelty cases in the media -I can't always resist lending my energies to the retribution process.
Would I do a spell for somebody else? Yes if they genuinely felt they couldn't do it for themselves and providing it was a reasonable request and they explained why it was important to them. However I would be sceptical of someone reluctant to put the effort in themselves. For magic to work it needs a good bit of both magical will and mundane effort behind it (why do you think my magical diets always flop?) and somebody who wants me to do all the work is likely not generating enough will of their own to make the spell work. If I felt they were being lazy I'd suggest they look for a witch with less of a workload and more patience!