Texting is an impersonal form of communication devoid of emotional nuance. So much emotion is lost when something is written down and can't, for example, be punctuated with a hug or a reassuring hand on the shoulder.
As people get better at texting it may become more expressive, even if its in the form of emoticons but perhaps most importantly it allows communication when other forms may be impossible or inconvenient, for example when ambient noise is too loud (as in a concert) or inappropriate (at church) or some other quite function.

Texting is causing motor vehicle and other accidents as people look at the screen and fail to pay attention to the road or what they are doing. This is dangerous and has not only ruined lives but caused many fatalities.
People simply need to learn not to do this, it's similar to drinking and driving. In addition all new technologies have an adjustment period as people learn when and how they are used appropriately.

It is one of the crudest forms of literacy shedding eloquence for ease of typing. Details and subtleties are reduced to just a few simple short words or even abbreviated to rudimentary letters and numbers. Unfortunately this is crossing back over to e-mail and other communications.
This may come down to the individual and hopefully people will learn to express themselves better. The next point could solve this one as well.

The act of texting is cumbersome, uncomfortable and inefficient as it is usually done on tiny mobile phones with miniature keyboards only fit for Tinkerbelle and Thumbelina.
Hopefully technology will make it easier and more efficient to write more detailed messages. Either with more advanced software or some kind of extendable or virtual keyboard.

People are texting instead of talking or meeting face to face reducing our social interaction and the simple pleasure of being in someone's presence with all its nuances and expressions both facial and verbal.
On the up side this is usually in situations where you can't talk in person to being with or hopefully you are using texting to make plans so you can actually meet the person face to face.

-Peter Ochabski