Some excellent comments here.
As someone who's been daytrading for many years, I can say I agree with Pabst's point about it's not a losing method so much as it is, losing traders trading incorrectly.
The blackjack analogy is great; I play at the Bellagio often, whenever I'm doing a trading seminar in Vegas, and by following the rules I usually can play for 6-10 hour sets at breakeven (I use Bloch's rules for basic strategy 100% of the time, after awhile it becomes mechanical). What's amazing to me is I can sit there for hours playing and watch dozens of players come and go, and NOBODY I've played with correctly follows basic strategy all the time. Why is this? Same reason traders fail. The winning techniques are there, but people don't want to (or can't) follow rules consistently.
And based on working with thousands of traders, I can say too that it's rare to find traders who 1) know how to daytrade the highest probability patterns consistently, integrating tape reading w/sectors and trin and specific micro-breakout patterns, and 2) have the discipline and skill to scale up/down based on the patterns and odds of the trade working out.
So I think it's mostly a discipline issue; many people either aren't willing to put in years to learn how it really works, and/or don't have the discipline and courage to do it right. It is *very* hard to daytrade correctly, even if you've been doing it fulltime for years.
Swing trading is easier, but can incur larger stops/losses as well, if done sloppily, so there's two sides to it.
#1 problem I've seen in traders is they overtrade choppy charts. They don't look for, and trade, high potential charts (for example on Friday I was actively daytrading SQNM ACAS BGP APOL etc, widest-range charts with volatility)... #2 problem is they don't realize how intense and hard this is.
I think it's much harder than being a corporate statistician/quality engineer, which I was for years, a long time ago, for example. Main reason is the emotions that get involved when you're trading w/thousands of your dollars on the line all the time.
Trading is all about taking a lot of shots, minor wins, minor stops are most of it, your edge is when there's a strong breakout (like doubling down on an 11 against a dealer's 5 - of course with trading there's no such limit as doubling, we can 10x our share size on high probability setups! great odds for us), then you can make moderate wins... the trick is, keeping all stops small, so the numbers come out like 40% small wins, 40% small stops, 20% moderate wins, 0% large stops. Thousands of trades over many years I've made, and that's the "solution set"... which means btw that having a broker w/low commissh load like ib is critical to success too.
Of all the many careers and things I've done in life, trading is the most exciting and most difficult. Kind of like dating a supermodel (but w/o the high maintenance, if you "get it" and play your cards, and trades, the right way).
Best wishes for success - gotta love this market, best since 99-01 I've seen for day and swing trades.
-k