j/k
You can use a service like SpyFu (www.spyfu.com) to get reasonably accurate information about competitors' bids. I have to stress _reasonably_ accurate, though. When I run my own site's numbers, it tends to inflate every data element by a fairly significant amount (c. 25%). Does that same error factor apply to my competitors? I have no way of knowing. But it does give me a benchmark, and can be valuable in tracking competitors' bid trends over time (are they bidding more aggressively? Less so? Expanding/contracting keywords? Etc...).
it tends to inflate every data element by a fairly significant amount (c. 25%).
I'll second this, my experience has been about the same, plus these sites always seem to attribute keywords to me that I've never bid on. I find it useful not as an objective tool, but just to see how advertisers relate relevant to one another.
If you want to have a good indication of cpc, use google's KW research tool, where you put different bid amount and it tells you expected number of clicks per day...
it tends to inflate every data element by a fairly significant amount (c. 25%).
I just ran one of my sites and it shows "Daily Ad Budget: $4.94 - $45.93"
The real daily spend for that one is around $650.
So it's not always the case of them getting it "pretty close".
They are good at getting basic keywords, but they can't possibly scrape ALL results for ALL sites in ALL niches.
I was worried about them a while back, but not so much now.
They are really good for brainstorming if you are out of ideas, but don't rely on the numbers.
As a side note (and don't take it personally), but if your real stats are close to what they are showing, that means you are not thinking outside the box enough with your keyword selection. In other words, you are only covering what most of the people in your niche are covering.