The only problem you might have with the last name and first name in different columns is the spacing between them. If the first name is in the lefthand column, a first name like "Abe" will have more space after it than will "Charlotte". The last names will be aligned on the lefthand side of the next column. It will look nice and clean with first names neatly aligned and last names neatly aligned but it won't look like it did when you had it all in one column.
Other options are
1) Have your original column of first & last names and another column which contains last names only. This new column would use text functions to strip off the first name; you wouldn't have to enter the last name manually. You would be able to hide this column and you would do your sorting in the Reorganize panel. The only problem is that you have to make a choice on how to strip off the first name and it won't be foolproof. A function that works correctly for Mary Jane Jones won't work correctly on Charley Van de Camp. The formula might be =RIGHT(B2,LEN(B2)-FIND(" ",B2)) which assumes the first space marks the boundary between first and last name.
2) Put first name and last name in separate columns then have another column that concatenates them with a single space in between. You can hide the columns with first and last names and display only the concatenated name. You would use the reorganize panel to do your sorting. You would have to unhide the columns to add new names to your table but this is the more foolproof method of the two.
In both of these, if you have a header row and put some text in that row (like "Last Name") to give the column a name, it'll be easier to sort by it in the reorganization panel. It'll be easier than trying to remember if "Column B" is the column with the last names in it.
3) My last and simplest idea is to use one column and enter the names as Last, First. Of course, if you ever want to sort by first name you will run into a similar problem. However, it will be foolproof to split them up if you want to do something similar to idea #1 because you will search for a comma, not a space, as the delimiter.
