GameRager: As long as you can space and sort easily why do you need more rows at the bottom? As you buy games it'll add more rows/spaces to accomodate.
DukeNukemForever: It's not about rows at the bottom, it's about total numbers of free rows. At the moment you get maximum three free rows and so maximum 15 (3x5) free spaces. To have more free rows means also to have more free spaces.
As example, you bought one or two adventure games and want to expand your adventure area, the easiest way would be to put an empty row after this area. Also you want that you every row has only one genre inside, so you need more free spaces (0-4 for every genre).
Are you sure about that? I sorted My Games by "Games I have downloaded all bonus content from" on the bottom, and "Games I haven't" on top. The first time I sorted them that way, I put the games on the very bottom row, leaving three empty rows in between them. When I came back to the My Account page later, the page had automatically created two new empty rows on the bottom, for a grand total of sixteen rows of five games. At this point I re-arranged the bottom group of games by moving them up two rows, so that there were now
four empty rows on the bottom. When I came back later after that, the page had automatically removed two of the four bottom empty rows.
In short, I think the My Games page just automatically appends two empty rows on the bottom, no matter how many you have.