I would think, from a team finance perspective, that front loading a contract wouldn't be in the best interest. Your hope hope in backloading a contract is that the rate of inflation "takes care" of the rise in yearly salary. Say a player gets a 5 year/ $50MM contract starting in 2014 with the following yearly salaries from '14 to '18: $8M, $9M, $10M, $11M, $12M. As the contract plays out inflation is inevitable, well, because inflation. At the end of the contract the hope is that $12M in 2018 has the same value as $8M in 2014.
Separate (kinda) thought: In my opinion the only place where front loaded contracts make sense is under a salary cap type league (NFL & NBA).
*talking myself in circles* I guess small market (or any other) MLB teams could be operating under a budget (salary cap). Thoughts?