You'd think I 'd find this on "Information is Beautiful" but got the link from a friend on Facebook. The images below visually display the patterns of "High Frequency Trading" (HTF), which can consist of high frequency trades to manipulate the markets.
"Aside from the fact that it is illegal to indicate a quote without a trade intent, this form of quote stuffing is in fact manipulative when conducted by HFT repeaters in specific "shapes" as it actually moves the NBBO actively higher or lower, in cases pushing the bid/offer range up to 10% higher without even one trade ever having occurred, simply by masking a big block order which other algos interpret as bid interest and pull all offers progressively or step function higher (or vice versa, although we have rarely if ever seen the walking down of a stock over the past 18 months)."
BATS "Flag Repeater". 15,000 quotes in 11 seconds, dropping the ASK price 1 penny each quote from $9.36 to $8.58 and back up again.
"The Crown". While not a large number of quotes, this NASDAQ/BATS Bidsize sequence was just too unusual to bypass.
NASDAQ "Blotter". One of the more unusual repeating Asksize cycles.