I've got at least two dozen direct ancestors that have alternate names and spellings. Sometimes it is only a matter of a letter, like Susanna/Susannah and sometimes it is meant to represent a post-immigration surname change like my vonAllmens who became Allmens when they came to the US from Switzerland. But mostly, all these alternate names and spelling represent plain old confusion. On one record the name is this on another record it is that, this time it was spelling this way, that time it was spelling that, etc. Didemia Beam is a good example. Note, Didemia is just the spelling I've adopted for her, there are about a dozen other variations out there. Her marriage record, death record, birth records for her children and census records all offer a different name for her: Didan, Dedamia, Didima, Didi, Diadame, Anna, Anni, Danni, Didaine, Didame, etc. Point is, the list of alternate names I have for her is longer than all the biographical information I've got on her.
Where do all these misspellings come from? Well, in the case of some ancestors, ones who had just immigrated to the US, I imagine it stems from the fact that they had a tenuous at best grasp of the English language. But in the case of Didemia this doesn't apply. She was Canadian, a native English speaker and came from a large and well known family in the (small) community where she lived in Ontario. I am more inclined to trust the spellings of her name on records from her girlhood there than after she got married and went to Michigan, yet the misspellings and alternate names are present even on her hometown records. I think it just breaks down to the fact that she had a unique name that could probably be easily mispronounced and misspelled. Something else to look for is the background of the spouse or head of household in which they lived. In Didemia's case, her husband was from Ireland and probably pronounced her name with a strong Irish accent which could account for some of the misspellings on records.
In any case, it has always been important to me to get an ancestor's name right and it drives me crazy when there are tons of alternate spellings because it really means no one knows what their actual name was. I think the reason why this is a big deal to me is because I have one of those names that can be easily mispronounced and misspelled. No one ever spells it right and hardly anyone pronounces it right (thanks a lot, Star Wars!). Adding to all this is the fact that there are two correct pronunciations, Lay-uh in the Jewish tradition and Lee-ah to gentiles like myself. I was recently invited to a family event by a relative who has known me her entire life and yet managed to misspell my name. It wouldn't be a big deal except that this is written on the type of document meant for scrapbooks and as a keepsake (it is an invitation to an event for every female in my mother's family and lists all of us, our connection to the common ancestor we are honoring, etc.). If anyone besides me where to get into genealogy this card would be a gold mine of information. Too bad there are errors on it (my name isn't the only one misspelled) which could easily be propagated and passed down.