Set product reviews limit and pagination
http://connect20.magentocommerce.com/community/Foundation_CustomizableFraudFilters
<reference name="product.info">
<block type="page/html_pager" name="product_review_list.toolbar" />
<block type="core/template" name="product_review_list.count" template="review/product/view/count.phtml" />
<block type="review/product_view_list" name="product_customer_reviews" as="product_customer_reviews" template="review/product/view/list.phtml">
<block type="review/form" name="product.review.form" as="review_form">
<block type="page/html_wrapper" name="product.review.form.fields.before" as="form_fields_before" translate="label">
<label>Review Form Fields Before</label>
<action method="setMayBeInvisible"><value>1</value></action>
</block>
</block>
</block>
</reference>
http://excellencemagentoblog.com/blog/2011/10/18/magento-collection-paging/