Read this:
http://www.entertainmates.com/conver...s_tips_016.asp
Makes a lot of good points about why people should make a real effort to use proper grammar. Effective speaking is the most key tool in a persons toolbox when applying for a job, mingling with guests at a party, or simply talking with older adults. Given txting as a way of speaking came about because of cell phones and the limited number of characters available to use in a conversation.(Not so much anymore with the new generation of smart phones but its already a habit for most.) Keep it there.
Forums have no character limit, WoW chat boxes do but its a fairly decent number that allows you to convey a lengthy message before having to send it. Adding that extra vowel or spelling out a long word like 'responsibility' isn't as hard as one would think and doesn't take that long either. If you want people to take you seriously in this world effective speaking, proper grammar, and maybe a few formal typing classes is the way to go.