I have noticed a rough correlation between the number of photographs and sources of an individual in online family trees and their "standing" in the family. Well, duh, you say. What did you expect. More prominent family members will automatically acquire more attention from descendants. We all want to be related to "important" people and so it is natural that the "important" person gets all the attention. But I think there is more to this issue than just ancestral prominence.
It is also common to find that pedigrees record only "direct line" ancestors, such as father to son or mother to daughter relationships with scant attention paid to the spouse. This often follows surname lines. I have written about this previously raising the "equal opportunity" argument that all of our ancestors deserve equal attention. But now, as I see this pattern in online family trees of adding sources and photos only for the prominent or direct line ancestor, I think there is more to be said about this issue.
First and obviously, your own surname plays a major part in determining your genealogical research interest. This is natural and is wrapped up with issues of identity and family traditions. But how we form our predilection to one family or another is a little more complex. In some families, I am certain that present-day interest in certain family lines is determined by the amount of genealogical interest in the past. We tend to follow the lines of least resistance and use information gathered by others and naturally follow those lines former researchers were interested in. In some cases, this interest has been established for hundreds of years looking back to the first immigrant or the first whatever in any particular family and this comes about as a result of looking at individuals, as individuals, and not focusing on families.
For example, it is not too uncommon when I mention being a descendant of the Mayflower passengers, to find someone who also claims that relationship. Many of these people can name the Mayflower passenger, especially if they have done any genealogical research, but few, if any, could name the wives of those same passengers or the names of any of the children outside of their direct line. What is ever more interesting is that many of these same people would have a difficult time explaining how or why they believe that this relationship exists with those same Mayflower passengers.
Now that I have become aware of it, I have certainly identified that tendency in my own research. I am finding that I have scanty evidence about the family members of even families that are close to me in time. So, it turns out that for the most part, genealogical research seems to be very narrow in scope. We focus on individuals rather than families. We tend to dismiss "collateral" relatives as outside our realm of interest. In fact, I have gotten into discussions recently about whether or not we should even care about these other "collateral" lines. But I see the same attitude applying to all the other lines that are deemed uninteresting, usually because there is no prominent family member.
I have referred to this phenomena when talking about doing the genealogy for those family members you like as well as the ones you don't like. But it is interesting to see that in online family trees apparently all of the family members make the same decisions about the same few family members and ignore the rest.
One thought that comes to mind is that genealogists tend to run in families according to some as yet unidentified family trait. In some cases, interest in genealogical research clearly arises because of contact with an older relative with the same interest. But in some cases, there are certain family members who become involved in the family history, not because of any contact with the older family member but for their own particular reasons. In my own Tanner family, there have been a succession of people who have written and published about the family starting back in the 1800s. I didn't know any of these people and didn't even know they existed until I started doing my own research.
Not only does this interest seems to run in family lines, it is also interesting to note that some families seem devoid of any interest at all for generations. There are no surname books, no histories, no records to speak of at all.
In my lines, we have a huge amount of information about some of the lines and no information at all about others lines. The lines with information attract more information and those with no information lie idle on the family trees. In my lines, for example, the contrast between the amount of information on the Tanner line and the lack of information on the Springthorpe line are polar opposites.
I guess the challenge we have as genealogists is to attempt to level the playing field, that is, to find information on all of the family members so that the family gets its genealogy recorded and not just certain individuals.