In theory, the more indicators you have pointing in the same direction, the less likely the price will go the wrong way. There are (at least) 2 problems with this.
Firstly, although some indicators may look very different, they might be measuring approximately the same basic information. This would mean that Indicator A will almost always give the same signal as Indicator B, and thus they don't really provide serious confirmation.
Secondly, even if you have 7 very different indicators, waiting for all of them to say Buy or Sell before trading might make for safer trading, but will also mean you could be waiting for a very, very long time for all of them to agree. If they only line up once every few months (probably at 2 in the morning), they may keep you out of losing trades, but you may almost never get a shot at a winning trade.
Yes, if it's really that good, you might set up an EA to place that "perfect trade" at 2 am once every few months. The problem with such rare trades is that it's hard to make money trading so rarely (unless you are a long-term trader, and I think most of us trade on much smaller timeframes here) without risking too much of your account. Personally, I would never risk more than 5% of an account even if I had an advance copy of Bernake's next interest rate announcement and it indicated a move that would correlate with 20 indicators.