Is it good practice to mix sales force with marketing team? If not then where to draw the line?

Definitely yes, market place has become more & more dynamic & two crucial departments though having different objectives should be aligned thus in practical or technical sales it's 'SMarketing' now & not mere Sales & Marketing.

Sales objective is to reach & surplus targets, ensure products are available & properly merchandised & reach the targeted number's that can be achieved only when marketing does it's job by ensuring proper ATL & BTL, planning promotions based on different target markets & cycles, proper stock planning, effective pricing etc

To have it there should be alignment of tasks, responsible for each other's objectives, ensure sales team provides crucial marketing intelligence, competitive scenario (At a outlet level) & promotions must be planned having a word with sales, there should be mechanism like ROI (Return On Investment) where sales person knows for example to take an additional space in an outlet/chain of certain value what is the value of sales is expected thus sales numbers is achieved along with expected return on such investment

:-)