Gnucitizen blog has an interesting post about Google Ajax Search API, a tool that allows you to integrate Google Search into your site and let visitors search Google without leaving your site. The post shows that this API could make life much easier for those who write malware and might facilitate their propagation.
"Web worms can use Google's infrastructure to propagate. If a malicious mind finds a vulnerability in WordPress for example and this vulnerability allows SQL Injection, a worm may be written to crawl blogs in search for this vulnerability and embed itself into everything that is vulnerable. Once a user visits an infected blog the worm starts another cycle.
Another worm might be able to crawl random sites and run generic Cross-site Scripting and SQL Injection checks and send the results to their master who will use them to release more advance worms.
Malicious minds can use Google technology and recently discovered vulnerabilities to create a BotNet that can be used for computational tasks, attacks, information gathering and pretty much everything else that the masters can come up with."
Cross-site scripting (Wikipedia)
Cross-site request forgery (Wikipedia)
Samy is my hero (MySpace worm)
More about Google Ajax Search API