The economy thing is quite nice about Scorched Earth, but it also is a pretty big potential game breaker.
Once you win a couple of rounds and get enough money to buy shields, you are practically indestructible. Very few things can penetrate a shield (especially the heavy-duty one), and it is likely that the other players don’t have them yet.
Thus, if you are not unlucky enough to get killed before your first turn, you activate the shield, which gives you at least 80% of winning the round (90% if you also bought parachutes!), which means you will get more cash, with which you can buy… more shields, and run away winning almost every round.
When playing with other friends we sometimes agreed to not use shields, just for this reason.