[eds]

Set it up so the participating sites can give away rewards to the people who beta test. Free accounts, discounts, whatever. You could organize all that.

Even if only a fraction of reviewed sites do it, you'll have enough people coming through that sites with nothing to give away will get attention too.

[jmonegro]

Not a bad idea... let's say they make, for example, 20 coupon codes for the 20 most useful reviews...