It's an evolution of language: it's fun and it has great creative potential.
Here's one example of a text-poem, by Ben Ziman-Bright, which I particularly like:
The wet rustle of rain
can dampen today. Your text
buoys me above oil-rainbow puddles
like a paper boat, so that even
soaked to the skin
I am grinning.
The length constraint in text-poetry fosters economy of expression in much the same way as other tightly constrained forms of poetry do, such as the haiku or the Welsh englyn. To say a poem must be written within 160 characters at first seems just as pointless as to say that a poem must be written in three lines of five, seven, and five syllables. But put such a discipline into the hands of a master, and the result can be poetic magic. Of course, SMS poetry has some way to go before it can match the haiku tradition; but then, haikus have had a head-start of several hundred years.
There is something about the genre which has no parallel elsewhere. This is nothing to do with the use of texting abbreviations. It is more to do with the way the short lines have an individual force. Reading a text poem, wrote Peter Sansom, who co-judged a Guardian competition in 2002, is "an urgent business ... with a text poem you stay focused as it were in the now of each arriving line."
Yesterday I saw a scruffy young man set up on a street corner downtown, sitting at a rickety table with an old typewriter, selling instant poetry. I wonder if he has a phone.