Remember that you have to add the +DM for skills and characteristics, and any environmental DMs such as range, local gravity, lighting conditions, visibility, wind speed, distractions and various forms of assistance such as guidance programs and so on.
Rolling a 2 only gives you an Effect of -6 if your skill is 0 and you have a +0 characteristic DM; if you have a skill rated 1 or higher, that adds to the number you roll; likewise if your characteristic is exceptional, such as if you had a characteristic of 9-11 (+1).
e.g. a character with Persuade-0 and Soc 8 (+0) who rolls 2 will get an Effect of -6 and probably have to run for his life. However, a character with Persuade-3 and Soc 10 (+1) gets a natural +4 DM to the roll, meaning his minimum Effect can only be -2 if he rolls a 2: a normal failure.
By the way, pity the poor guy who tries a skill Untrained and who has an unusually low characteristic: the character with no Persuasion skill and Soc 5 (-1) suffers a -6 Effect if he rolls 6 or less!