If an institutional Investor (e.g. a Mutual Fund company!) wants
to buy a bunch of stock, it is obvious that they CAN NOT simply log
on to an order entry system and enter a single Market or Limit order,
like a retail investor would. If they did, they would get horrible
order execution (huge slippage) and/or unfilled orders, respectively.

That is my theory based on my model of how the universe works :-)

Your job for this question is to put together a persuasive argument
either supporting or debunking my theory. You must include anecdotal
and hearsay evidence gathered from the Internet and other sources.
You must also include a brief profile (based on the evidence gathered)
of the typical employee in charge of entering trades for institutions
and typical rules and procedures they are bound to follow, if any.