A developer posted this response a few days back and states the facts quite eloquently in response to your question:
"You probably don't want to install everything you see in the market. Keep only what you use every day. If an app seems to affect your battery or performance, contact the dev and file a bug report.
Most of the task managers are horribly written, and in the hands of anyone other than someone who knows what every single service is and does on their phone, can cause lots of problems.
The proliferation of task managers in the market comes from people who having been on other platforms which needed them, and assumed the same is true for Android. It's not. It's linux-based. It has amazingly good memory management.
Remember, it's better to keep your system lean and clean than to rely on a task manager."
Also just an FYI, stay away from any anti-virus software for the Droid. None is needed and as reported dozens of times here in the forum, they create serious loss of functionality and rapidly deplete your battery. I hope this helps you.
