I've gone to a few FNM drafts, and it's structured as three qualifying matches, followed by a single-elimination tournament for the top 8.
Do all these games affect your DCI rating?
Magic tournaments are in the process of changing from using DCI Rating to "Planeswalker Points", which strongly rewards players for simply playing Magic (with DCI rating, NOT playing was sometimes best), while still rewarding skill/winning, although to a much lesser extent. You can read all about the change in this article on the Magic the Gathering website.
In spite of the change, the answer still stands:
The Planeswalker Points website says that FNM is a 3x multiplier on the points you earn. Event multipliers range from 1 to 12:
Here are examples of the different event multipliers available at events: 1x: Sanctioned Magic tournaments, Prerelease events, Launch Parties 2x: Game day events, WPN Premium Qualifiers 3x: Friday Night Magic, Grand Prix Trials, WPN Premium Tournaments 5x: Pro Tour Qualifiers, National Qualifiers 8x: Grand Prix, National Championships 12x: Pro Tour *, World Championship
Yes they do, but they have less impact on your rating, and a less serious level of rules enforcement, than tournaments at a higher level of play.
From the Wizards site:
FNM events are 8k tournaments and have a Regular Rules Enforcement Level (REL).
Here's how that 8k figure factors into the calculation of your rating change after winning/losing a watch:
The Elo player-rating system compares players’ match records against their opponents’ match records and determines the probability of the player winning the matchup. This probability factor determines how many points a players’ rating goes up or down based on the results of each match. When a player defeats an opponent with a higher rating, the player’s rating goes up more than if he or she defeated a player with a lower rating (since players should defeat opponents who have lower ratings). All new players start out with a base rating of 1600. The DCI uses the following equation to determine a player’s win probability in each match: Personal Calculation: 1 Win Probability = -------------------------------------------------------------- 10^(( Opponent’s Rating–Player’s Rating)/400) + 1 This probability is then used to recalculate each player’s rating after the match. In the equation below, players receive 1 point if they win the match, 0 if they lose, and 0.5 for a draw. Players’ new ratings are determined as follows: Player’s New Rating = Player’s Old Rating + (K-Value * (Scoring Points–Player’s Win Probability))
For comparison, there are lots of more competitive tournaments at the 16k level, and Premium tournaments are at 32k!