'Whereby' is not the same thing as 'where'. People using the word 'whereby' to sound intelligent only sound silly when they use it wrongly. Often, people also use 'whereby' when they mean 'wherein'. (This all drives me bats, by the way.)

In the effort to sound more impressive, many people use big words they don't quite understand, but words have nuances, and similar-sounding words don't always mean the same thing. 'Angry' is not the same thing as 'annoyed' or 'furious', for example — there are shades of meaning there.

There's nothing wrong with using simple language and clear speech, as long as it gets your point across. Think about it: cheap clothes made of poor quality material are often dressed up with fancy decorations and trimmings; a plain, well-cut shirt made of excellent fabric needs no disguise with ric-rac and beading and sequins. You can see the quality of the well-made item right away. Tons of cheap trimming, on the other hand, doesn't disguise poor material and cut at all. ;)

Also, while you're at it, think about pacing in your writing. Vary the length of your sentences and paragraphs. Reading a piece that's all long, involved run-on sentences isn't fun, and more often than not, complex sentence structure obscures your meaning. Also, when you write long sentences, grammar tends to suffer, unless you're really good about proof-reading and know your grammar instinctively.

Exclusively using short sentences, on the other hand, makes your writing choppy. This again makes it hard to follow your train of thought.

Writing is really about communicating, so communicate! :)