Back to Back Ticketing
 

Flying say BOS-EWR Saturday and return Monday to take advantage of the United Special fare. Book a sperate ticket EWR-BOS, fly back to BOS
Saturday, fly BOS-EWR Monday return portion of ticket 2 and then fly EWR-BOS Monday night return portion of ticket 1. This is clear back to back ticketing.
What if on ticket 2 Saturday you book say EWR-TPA and return Monday then take your EWR-BOS return is this really still back to back ticketing. say your intention is going to TPA from BOS and you are just taking advantage of the low special fares, not trying to circumvent the 2 day layover on your BOS-EWR ticket. Where do you draw the line on this.

Presuming that the conditions of ticket 1 include a minimum stay provision, then yes, this is the very definition of back-to-back ticketing.

That is end-on-end ticketing and is completely valid.

What is the purpose of the minimun stay requirment. Well, I can see in this case they are trying to fill seats on slower travel days, Saturday, Monday and Tuesday, where Sunday is usually has less open seats. So how I am hurting the airline buy buying 2 roundtrips. I look it is a ticket is a ticket. How does back to back ticketing hurt the bottom line of an airline.

Airlines ban back to back ticketing, because if they didn't then they would lose a lot of revenue from business customers.

They don't really care about you doing it if you are a tourist but the rules have to be harsh to prevent 1,000,000 traveling consultants like me from stopping buying M-F peak returns and instead flying on two cheap nested tickets instead.

(Mind you, BOS-NYC-BOS and NYC-BOS-NYC on two separate airlines is undetectable and I'm sure plenty of people do that.)