Recently it’s become plain that Twitter plans to add Facebook-style filtering to the Twitter timeline. In other words, Twitter would reserve the right to add or remove tweets from your timeline, rather than sending through every tweet from every account you follow (and none from those you don’t).

Twitter’s stated goal is to make your timeline more engaging, which makes sense based on how they’re monetizing the service. Twitter charges advertisers to promote content, which like any other advertising requires a big block of people constantly paying attention to be worth anything.

For some users, filtering like this means nothing less than the end of Twitter. That may seem overblown, but I think it’s a fair assessment. To be specific: filtering the timeline changes Twitter from a communications service into a news or entertainment service, which is inherently less valuable to me as a Twitter user.

I’ll step back and define some categories:

Communications services involve connecting to a network, then sending or receiving over that network with any other member, as a peer. Examples include mail, phone, ham radio, text messaging, email, IM, and Skype. Connecting to the network may involve cost (like phone service) or registration (like ham radio), but once connected you can send and receive to and from anyone. Communications services are often judged by the completeness and availability of the network (vs. dropped calls or missed emails).

News services involve curated content made by producers and received by consumers. They might use their own network (like newspapers or television) or piggyback on communications networks (like email newsletters or sports updates by text), but the content itself is their primary concern. News services are often judged by the accuracy and timeliness of their information. Choosing whether to cover a particular story is considered an editorial decision, but news services can get in trouble for presenting edited content as truth. (Thus “recorded earlier” notices, or “this interview has been condensed”.)

Entertainment services are like news services, but go a step further; they curate content to be engaging, without the requirement to be true or accurate. Entertainment services often go hand-in-hand with news services, delivered by the same network (like television) or even sharing the same packaging (like newspapers).

The lines between these are fuzzy, but one yardstick to use is the kind of complaints you’d find reasonable in each case. We complain to the phone company when we can’t make a call, but we don’t complain to them about getting 20 tech support calls from family each day. We complain to ESPN when they don’t cover enough soccer, but not that a broadcast game didn’t feature enough goals. Conversely, if the phone company blocked your aunt’s tech-support calls or ESPN added CG goals to the game, that would be unacceptable. You wouldn’t see it as “more engaging content”; it would make the service inherently less valuable to you.

At its core, Twitter is (and has always been) a communications network. It’s a broadcast network, like ham radio, but if I’m sending and you’re listening you expect to get my message. It’s a free service, like IM, but you’d rebel if you started receiving IMs from advertisers or found companies on your buddy lists without adding them. It delivers news and entertainment content, like the mail, but you’d be shocked if the post office rearranged your newspaper or tucked another DVD in the Netflix sleeve.

The justification Twitter gives for adding tweets to your timeline – hey, these are still real tweets, not ads! – misjudge the category they’re in. If CNN swaps news stories with other news, that’s an editorial decision we expect them to make. If AT&T connects my call to a random neighbor because my wife didn’t pick up, that’s bizarre and unexpected.

Considering it this way, I’m not surprised at all that Twitter users are threatening to leave if filtering is added. I’ll probably leave myself, and look for a social communications service that knows what kind of network it is.