Depends on the purpose of the page too.

EG: If your call to action of a page is to call a phone number, then a high bounce rate is acceptable due to the purpose being met.

Bounce rate is a great metric to measure improvements and calls to action. Try and get it lower by all means, but there's no silver bullet with bounce rate or magic number. 
As David mentioned, a bounce could mean elimination of an unqualified lead, either way it's quality over quantity in most cases.

Good luck.

Thats correct in most cases:

It works likes this: a robot wants to vists a Web site URL, say http://www.example.com/welcome.html. Before it does so, it firsts checks for http://www.example.com/robots.txt, and finds:

User-agent: *
Disallow: /

The "User-agent: *" means this section applies to all robots. The "Disallow: /" tells the robot that it should not visit any pages on the site.

Robots can ignore your /robots.txt. Especially malware robots that scan the web for security vulnerabilities, and email address harvesters used by spammers will pay no attention.

More information available here about:

http://www.robotstxt.org/