Letter

can we using this kind of shortcut in our formal letter?
hahhaha~ this picture shot by me on last 2 week on pinky book...
a book which circular by her boss...on learning how to write a proper email or letter to clients & customers
we just read it a while but feel so boring indeed
but interested about this page only....
something to share with all of you...

MSG = message
JIC = just in case
CUL = see you later
FAQ = frequent asked questions
IMHO = in my humble opinion
BTW = by the way
TTFN = tata for now
BRB = be right back
GTG = get to go
LOL = laugh out loud
OIC = oh i see
TTUL = talk to you later

actually during msn, the most frequent used shortcut is
1. GTG
2. LOL
3. OIC
4. BRB (this one i always forget but now i know wat is this mean, hahah)