If there's any correlation between the recently killed Kin and discontinued T-Mobile Sidekick -- aside from Microsoft having a hand in both discontinued phones -- it's that they tried to distinguish themselves from both high-powered smartphones and simpler feature phones.
That idea will soon become irrelevant, and here's why:
Social networking is clearly a hot trend in smartphones. Palm's WebOS phones led the pack with Synergy, a program that lumps contacts from e-mail, messaging applications and social networks into one view, while also merging instant messages and SMS into a single feed. Then came Motorola's Motoblur, a user interface that merged Facebook, Twitter, MySpace and other networks into a single feed on the homescreen.
Now, it seems like everyone's getting on board. HTC's Sense interface gained Friend Stream, whose function is self-explanatory. Motorola's Droid X won't back Motoblur specifically, but something like it. Down the line, you'll see Windows Phone 7's People Hub, a running feed of status updates and photos from friends. Even the buttoned-up BlackBerry is joining the fun, as the BlackBerry 6 operating system will include a "social networking feeds" application.
The problem is that smartphones require expensive data plans that turn off people who want less. The Kin, which Microsoft called a "social phone," was an outright failure largely because its $30 monthly data plan didn't sync with the Kin's lack of features. The Sidekick had special price tiers that included data and text, and it had a long and healthy run -- last year's data snafu notwithstanding.
Increasingly, it's becoming possible to get a smartphone for the same monthly cost as a Sidekick. Earlier this month, AT&T put an end to unlimited smartphone data plans, but it also introduced a low price tier of $15 per month for 200 MB of data. That's not ideal for watching video or streaming music, but it can certainly handle Facebook and Twitter, thereby making smartphones more accessible than ever. Other networks may follow AT&T; Verizon is already considering it.
Even if T-Mobile gives the next generation of Sidekicks a special monthly rate, it won't look much different than the low price tier AT&T offers. Therefore it'll have to compete with all other social network-friendly smartphones. So I'm not surprised that a rumored follow-up to the Sidekick, said to be coming in May and called the "Sidekick Twist," sounds a lot like a smartphone, with Android 2.1, a 1 GHz processor and 4.3-inch Super AMOLED display.
To put it all another way, the line between smartphone and feature phone is blurring, and phones that try to split the difference will get lost in the obscurity.