Or undue speculation depending on the context.

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Note added at 6 hrs (2012-07-26 23:02:15 GMT)
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Some references:

Critères
(4) Lorsqu’elle décide si l’inscription prévue au présent article est dans l’intérêt public, la Commission tient compte des éléments suivants, à savoir :
[...]
d) si des mesures appropriées ont été prises pour prévenir la manipulation et la spéculation abusive;
http://www.e-laws.gov.on.ca/html/statutes/french/elaws_statu...

Factors
(4) In making its decision as to whether registration under this section is in the public interest, the Commission shall take into account whether,
[...]
(d) adequate measures have been taken to prevent manipulation and excessive speculation;
http://www.e-laws.gov.on.ca/html/statutes/english/elaws_stat...
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Inscription
15(2) Lorsqu'une personne ou une compagnie désireuse d'exploiter au Manitoba une bourse de contrats à terme de marchandises présente une demande en ce sens ou qu'une telle demande est présentée en son nom, la Commission autorise l'inscription si elle est convaincue qu'elle ne porte pas atteinte en ce faisant à l'intérêt public. La Commission tient compte, en rendant sa décision, des éléments suivants, à savoir :
[...]
d) si des mesures appropriées sont prises pour prévenir la manipulation et la spéculation abusive;
http://web2.gov.mb.ca/laws/statutes/ccsm/c152f.php

Registration
15(2) Upon application by or on behalf of a person or company wishing to carry on business in Manitoba as a commodity futures exchange, the commission shall grant registration to the person or company where it is satisfied that to do so would not be prejudicial to the public interest, taking into account whether
[...]
(d) adequate measures are taken to prevent manipulation and excessive speculation;
http://web2.gov.mb.ca/laws/statutes/ccsm/c152e.php
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From the Bienvenue au Centre for legal translation and documentation at the University of Ottawa:
manipulation and excessive speculation
manipulation et spéculation abusive
http://www.ctdj.ca/lexont/def_m.htm

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Note added at 6 hrs (2012-07-26 23:27:29 GMT)
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Oops, the last sentence should read:
"From the Centre for legal translation and documentation at the University of Ottawa"
[bad cut & paste :o]

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Note added at 1 day5 mins (2012-07-27 16:43:59 GMT)
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After watching the video, I think that my primary suggestion – "excessive speculation" – fits the bill. Here are some English-language references:

[...] pioneer asset manager Benjamin Bingham on financial transactions tax to curb excessive speculation and high-frequency trading, closing tax havens, raising capital reserves, breaking up too-big-to-fail banks and more.
http://www.ethicalmarkets.tv/

The theory is that the tax would discourage excessive speculation, thereby reducing the excess volatility that some contend arises from those activities.
http://www.caymanseminar.ky/materials/White_Paper.pdf

Just weeks ago Britain's financial regulator, Adair Turner, the Chairman of the Financial Services Authority, proposed a global tax on financial transactions to curb excessive speculation and executive pay.
http://www.huffingtonpost.com/kyle-g-brown/beyond-the-tobin-...