Advantages and disadvantages of business intelligence?

Sometimes it can be hard to quantify the ROI on BI software as the returns come indirectly through the better informed workers and decision makers across the company. For example analysing sales data might show hidden links within your customer base and so reveal how to better retain old customers and attract new ones. Mixing this with your financial data might then show that one group of customers cost a lot more than another, despite equal revenues, allowing you to further refine your targetting. More than increasing profits, well informed strategic decisions make the difference between the growth and collapse of a company.

Clear advantage of Business Intelligence is that if you have it - you have a clue of what is going on in your company, what are interesting trends, what are predictions (forecasting) and last but not least, you can be alarmed on time if something is wrong (if you are let's say CEO you don't have to wait for some report 2 weeks and then realize that you should have known that information 2 weeks ago).

Disadvantage - only one, you have to pay for it, for services and BI tools. That's the only one.

I am participating in a discussion on BI in another venue. While we see BI as a much needed tool for a business to be successful we see a number of companies not using it effectively or ignoring the results.
The one problem you have whether doing BI with people or software is that it is based on the collection of data and in most cases by the time the data is collected and analyzed the event has passed and you are in a reactive mode. If the time to collect and analyze can be sped up so that you are reacting more in real time would make it a better tool.
Remeber that it is a tool and not to place all your decision on one tool.

The biggest problem with BI is that it provided 20/20 hindsight and triggers rules based on previous internal scenarios.