RE:Daily swings and your TFSA - OTteebore...what a great question!!
As pointed out by zt there are statements in the tax code dealing with it. That said there are laws covering just about everything you do in life. From time to time on a long bicycle ride I stop to have a pee on the side of the road. This is illegal under the Highway Traffic Act in several provinces and in most States in the US. I don't know anyone who has been charged with this offence and in fact one time I was doing it a few years ago and an RCMP cruiser passed by me and the officer smiled and waved!!
So the bottom line here is it really depends on how big you are and whether somebody complains about you or not. Further, in the case of a TFSA, you do not report these trades on your income tax and additionally, financial institutions reporting on TFSAs is essentially limited to tracking the money going in and out of a TFSA, not individual trades. Also, you will not receive a tax form showing your trades for the year like you would in an unregistered account.
Bottom Line?
Unless you have given CRA another reason to look into your affairs or you really peed off somebody who would report you, there is little to be worried about.