unlike with AdSense for content ads, you can endorse your referral products
by calling attention to the button or text link. If you believe in the
quality of the product that you're referring, feel free to let your users
know.
Generally, visitors should only click on Google ads if they're interested
in the services being advertised. Encouraging them to click on your Google
ads, either directly or indirectly, can lead to inflated advertiser costs
-- and can cause an account to be disabled.