to mob: Keep in mind mate, not everyone uses word or intstalls open office, etc. Some rely on the tools they are given.
to Hellblazer: if you don't have word etc available, there are a few other locations you can go to do spell checking. Gmail is a prime example of real time spell check. Mozilla Thunderbird also has a spell check module that can be installed. Just keep in mind that unless you run a word processor, your grammer can still be a weak link also.
I'd like to see the feature, but usually type everything up in notepad++ first anyways (sans spellcheck) before posting.