Before/after example. This is usually done with a for/each loop from the
bottom up.

Dim LastRow As Long
Dim i As Long

   With Activesheet

       LastRow = .Cells(i, "A").End(xlUp).Row
       For i = LastRow To 2 Step -1

           If .Cells(i, "A").Value <> .Cells(i-1, "A").Value Then

               .Rows(i).Insert
           Ed If
       Next i
   End With

You could use this udf

Sub InsertRows()
Dim cRows, i, WhichColumn As Long
Dim TempColumn As String

TempColumn = InputBox("Which column do you want to compare?")

'Can input either the column label,or the number of the column
If Application.WorksheetFunction.IsNumber(TempColumn) Then
   WhichColumn = TempColumn
ElseIf Application.WorksheetFunction.IsText(TempColumn) Then
   WhichColumn = Asc(StrConv(TempColumn, 1)) - 64
End If

'Get a count of the rows
cRows = Cells(Rows.Count, WhichColumn).End(xlUp).row

' Walks backwards to avoid the row numbers changing
For i = cRows To 3 Step -1
   If Cells(i, WhichColumn).value <> Cells(i - 1, WhichColumn).value Then
       Cells(i, WhichColumn).EntireRow.Insert
   End If
Next
End Sub