The math = 1 monthly screening series = 12 screenings a year x 50 cities = 600 new screening opportunities in the US.
And if more than 1 filmmaker decides to organize a screening series in each city, the total number of screening opportunities will go up. For example, if in Chicago let's say, 3 filmmakers decide to create 3 separate monthly screening events, the total number of screening opportunities will go up to at least 36 in Chicago (higher if each month's event in one or all series includes several shorts as opposed to just one feature). So, if that approach gets duplicated in 25 major US cities (3 filmmakers in 1 area producing 3 monthly series, equaling 36 screenings a year), the total number of new DIY film screening opportunities in the US will go up to 1200 (25 x 36 = 900 + 300 [12 x 25 = 300 (the other 25 filmmaker/programmers from cities where there is only 1 monthly DIY film screening series]).
What exactly is a monthly screening series you ask? Basically you find a place where you can put a video projector, speaker(s), a DVD player, a large screen, chairs & then you organize a screening of a film or films at least once a month at that place. The films that you would screen at the monthly event would come from your own filmmaking work, films of friends, other filmmakers that you can contact through their blogs or sites, & films that you hear about through festivals or other sources - basically any film & filmmaker that is interested in the opportunity & that you like (films that you like, & also filmmakers that you like - people that you can work well with, relatively trouble-free people, will save on headaches). This could be a non-profit event funded by donors, a self-funded project that could be a useful resume item or advertisement for the filmmaker/programmer or this could be funded through a combination of private/personal $s, donors, ticket sales to the event, sponsors, etc.
A single screening can be produced for $0 - $500. $0 if you own all the gear needed to screen the movie or if you can get free access to the gear, and if you use free or very cheap/already existent/owned by filmmaker/programmer publicity avenues (e-mail, blogs, etc., maybe $20 for some fliers can't hurt), & if you do not pay a screening fee to the filmmakers (it would be far better if you did). In the DC area all the gear needed to put on a screening can be rented for around $300. So my $500 figure for a screening includes some money for advertisement, and a fee for the filmmaker whose work is being screened at the event.
As far as classifying this type of event into the screening categories that are popular in the indie film world at the moment, the DIY screening would be similar to a film festival screening as far as film festivals and distributors are concerned. However, the event - 1 screening a month - most likely will be comparatively a lot smaller in its public awareness impact than a film festival or even a short theatrical run; it should not pose a competition threat to people who operate/program festivals & theaters, & thus filmmakers who participate in a monthly screening series should also be able to participate in film festivals, & also deal with distributors.
As the DIY music scene of the 80's & the 90's & beyond was built through musicians organizing their own shows (the music - hardcore punk rock being one type - did not easily fit into the existing public performance opportunities, as some DIY films might not), the DIY film scene that is possible (and is already happening on a small scale) through relatively inexpensive digital filmmaking, inexpensive publicity through the web, etc. should develop - would be useful to develop - a nation wide, interconnected, network of screening opportunities. Such a thing would be very useful for wider distribution/availability of DIY movies, & for building filmmaking careers.
And, it is also just a lot of fun to show a movie you made, or a cool movie by another filmmaker, to people in your town. If you don't show it, most likely many people in your area might never hear of that movie.
Anyway, something for you to think about if you are an indie/DIY filmmaker & you are interested in sharing your movies, or other DIY movies that you like, on a large screening with the public . I am doing it in Silver Spring.
Let me know if you decide to do it in a city near you, we can keep in touch and build a DIY film screening circuit.