Benefits of pay-per-click search engine marketing include, but are not limited to:

1. An immediate response. Your ads will show within minutes.

2. Great for launching time sensitive campaigns and for testing new/different offers.

3. Can find low hanging fruit in the form of "Long Tail Keywords" that are cheap and highly converting, but would otherwise be too specific to build an SEO strategy around.

4. Alternatively, pay-per-click might be the only way to rank for some of the more competitive and general keywords.  I don't typically advocate this strategy, but there are some cases where the best keyword phrase is very popular, converts well, and is extremely difficult to rank for naturally.

5. Analyzing the effectiveness of a pay-per-click campaign (landing pages, ad copy etc.) will help determine what will be effective in a natural search campaign saving you the time and resources required in a long term SEO strategy.

What other benefits have you found from pay-per-click?