I-829 Denials

I was just going through the USCIS website.
While looking at the stats of I-829 denials in FY2008 and FY 2007, the number of denials seems very large (approx 25%). I understand that these I-829 petitioners include indiviual investors too, it will be very helpful to know what is the expected rate of denials for investors through regional funds?

If I assume all the denials are for RC investors, than applying through EB5 might not be a great idea, which means you invest 500,000 and get green card for only two years.

FY 2007 (I-526): 473 approvals, 148 denials.
FY 2007 (I-829): 111 approvals, 49 denials.
FY 2008 (I-526): 640 approvals, 120 denials.
FY 2008 (I-829): 158 approvals, 58 denials.