Older readers and purists do not much like the shorthand that is creeping into English thanks to internet chat rooms and messaging services. To them, LOL, meaning 'laugh out loud', will never replace merely laugh, nor is it likely that they will say 'BTW' instead of 'by the way'. For all the correctness, though, they will never be able to stop the evolution of a language, particularly one so homogenous as English. With technology increasingly integral to our lives, it is inevitable that what happens online will become one with everyday living.
English derives from the fusion of European languages and its vocabulary has expanded with the contact of speakers with other cultures. It is only the third most natively-spoken language in the world behind Putonghua and Spanish, but there is no other that has been as widely embraced and learned. As the lingua franca in many regions, it is inevitable that some words and terms in local use should be assimilated. As the prevalence of the internet spreads, that process will be furthered.
The Oxford English Dictionary lists more than 250,000 distinct words, not including technical terms, acronyms and slang. It is a number that grows by the hundreds with each new edition and as long as the language flourishes and expands its reach, this will always be the case. There are additions many of us will never have heard of or will use, but will have available for those moments when no better word will do. In the fast-paced world of the instant message, where time and space count, TMI, for 'too much information', POS 'parent over shoulder' and IMO 'in my opinion' are handy indeed.
It is a trend some may object to, but should not try to stop. As messaging gets more sophisticated, some terms will die out, while others will thrive and burrow into everyday language. Some will not easily be ignored, while others will be forgotten. The use of such terms in messaging should not be seen as a threat.