I was going to buy some pasteurized, natural, no preservatives added cider and throw some honey in it to bump up the gravity. I plan on pitching some pretty voracious yeast, so figure any bacteria in the honey has little chance, but I wanted to check with the wealth of experience from this site. What are my chances of having an issue with the bacteria in the honey? (me: first time cider, long time beer). When I add honey to beer, I throw it in as late as possible so as not to drive off the aromatics. So although I could heat the honey before using it in cider, I'd rather not, and keep more of the honey's aroma.
No, it is not necessary. In fact, many argue that it's much better to not heat it, as pasturizing the honey often time strips the honey of it's aroma & heat-sensitive aromatics. I would add the unfermented cider and the honey and stir it like crazy with sanitized spoon or other mixing device. Much like the "no-heat" meadmaking method. This will help integrate the honey, and you won't have to worry about getting everything back down to pitching temperature. I've made several batches of mead this way and have had no problem with bacteria-related off-flavors. At a healthy pitching rate, the Saccharomyces will out-compete just about everything in the must, and the high alcohol and low pH will prevent most of what's left from getting a foothold.
I don't know where djr obtained his information to say "Crystallized honey is more likely to spoil (ferment)". Honey will only ferment if it is robbed from the hives before the bees have ripened /dried it to less than 18 percent moisture. Commercial bee keepers wreck their honey of it's enzymes by heating it in order to kill the spores which only become activated if unripened honey has more than 18 percent moisture. Honey crystallizes because of the high glucose to fructose content and it is natural. To stop crystallization the honey is heated and ultra filtered. Always remember the hive temperature is a constant 37-38 degrees Celsius and any heating beyond that must be detrimental to it's beneficial qualities.
Honey is usually processed before use to remove wild yeasts, not bacteria. They can contribute to off flavors but will probably be out competed if you pitch vigorous yeasts. If you are worried you can heat the honey-water to 170ish and leave it there for 15 minutes, that should take care of any microbes without driving off much flavor. I would be interested to know how it goes if you don't do any processing though, I have been considering trying this myself. I wouldn't be worried too much about infection, as I know sometimes mead is made with only the wild yeasts that occur in the honey (but this can be highly variable).
I have not not (yet) done what you are planning to do, but I would heat the cider and honey to a pastuerizing heat (I think about 63 Celcius should do for honey but I'm not sure about cider; you don't need to bring it to a full boil). Honey dissolves easier when it's hotter and it will also pasteurize your must before you pitch. I usually do this when making mead.
If you don't want to pasteurize, then you could just put your jar of honey into a bowl of hot water for about 10 minutes. I doubt it gets hot enough to destroy any flavours that are damaged by high temperatures, but it will warm the honey just enough to pour and dissolve easier (I also do this when making mead, just so that it pours easier and faster). Warming the cider will also probably help with dissolving the honey.
I personally would be too worried about bacteria in the honey. I would be worried about the cider having wild yeast and bacteria from the pressing process. I recommend adding potassium metabisulfite or campden tablets(~50-75ppm) the cider 24-48 hours before you intend to pitch your yeast. This will take care of the bacteria and yeast and you should be able to add the honey without heating it just before you pitch the yeast or if you are concerned you could add the honey when you add the sulfite.