You can use row-fluid instead of row, then you won't have this problem. (for previous versions of bootstrap)
I am not sure of recent versions 3, any way :
The issue is that the first column should not have half a gutter on the left, and the last should not have half a gutter on the right. Rather than use some sort of .first or .last class on those columns as some grid systems do, they instead set the .row class to have negative margins that match the padding of the columns. This "pulls" the gutters off of the first and last columns, while at the same time making it wider.
For more information on this Why does the bootstrap .row has a default margin-left of -30px?