Does pump'n'dump spam really work ?

Simply said: yes it does. Limited, but it works.

The long answer:
Sometimes you receive unwanted e-mail (spam) telling you some company will
make a huge stock profit the next few days because some breakthrough or
other reason that they will become worth a lot more. It looks like a genuine
stock tip. But you never asked for it. You then ask yourself "what's the
catch".

The catch is that the spam is the reason of the stock profit. The idea of
this spam is to artificially inflate the price of a stock because of huge
trading and then use this to make a profit. The exact story is much better
explained at

http://ga.to/mmf/SpamExplained/Pumpndump.html

so I will not repeat that here.

December 4th 2001 I got spam about the BTLY stock. I'll repeat the first bit
here:

MAJOR CONTRACT ANNOUNCEMENTS AND HUGE NEWSLETTER COVERAGE THIS WEEK FOR BTLY!

This wednesday, BTLY will be profiled by some major
newsletters along with the release of significant
news regarding explosive sales for the Company.

Sort of "act now, this is a sure winner!".

And then I looked up the symbol on finance.yahoo.com, and got to:

http://finance.yahoo.com/q?s=BTLY.OB&d=c&k=c4&t=5d the 5 day trading and
http://finance.yahoo.com/q?s=BTLY.OB&d=c&k=c4&t=1d the 1 day trading.

(Funny how yahoo likes short url's)

so it looks like it sort-of-worked.

If the perpetrator bought their stock at $0.10 and sold at $0.13 (given the
sharp edges in the graph that sounds reasonable to me, but I'm no
stock-expert) then he/she made a 30% profit.

Later addition: I can't get "historical" charts of a day on Yahoo, but I can
link to historical trading volumes which show that December
4th was a day with exceptional trading.