I was playing w/ some time series data that had gaps in it. When I created a line graph of this I received broken segments or 'gaps' in my line for the missing dates. Not wanting to show this to my end users I changed the formatting option for Special Values to 'Hide (connect lines)'. This is great and it gave me what I wanted but the more I thought about this, the more I thought connecting these lines w/ the same format of the rest of the contiguous data can be misleading.
Let's suppose that sales on March 15th was 100 units, then on April 12th they sell 250 units in between of which we do not have the data. Tableau's current behavior would draw a perfectly linear line, formatted exactly the same as the rest of the line, between the two points. During this time however, sales could have been happening and varying wildly so we really don't have a complete picture of what happened between those dates.
What I am suggesting is that, to call attention to this missing segment as not a normal segment of the time series, offer formatting options for the missing segments which are joined together when choosing the 'Hide (connect lines)' formatting option. Maybe default to a dashed line?
I can provide screen shots if this becomes something folks are interested in. Vote it up!