I would like to create a Salesforce lead based on info I gather in a web app.  Questions...

1- If I use the Salesforce API, what is the easiest way to prevent duplicate leads/accounts from being created? Is the email address for an account automatically restricted to unique values?

2- I see that there are some AppExchange apps that convert emails to leads.  Anyone have success with this? (advantage: don't have to write code)

3- Can I easily use an Apex Email Service to get leads generated via email? 

I would like to create a Salesforce lead based on info I gather in a web app.  Questions...

1- If I use the Salesforce API, what is the easiest way to prevent duplicate leads/accounts from being created? Is the email address for an account automatically restricted to unique values?

2- I see that there are some AppExchange apps that convert emails to leads.  Anyone have success with this? (advantage: don't have to write code)

3- Can I easily use an Apex Email Service to get leads generated via email?