If I buy apps and then format... do Ihave to rebuy?

[xythil]

so if I buy the backup app... but then restore my device or switch SD cards or change devices to another android phone...do I lose the app? DO I have to repurchase it?

How does this work? is it linked to my account so that I always can Download it?

 

[cpjr]

Its linked to your gmail account, so you can transfer easily without rebuying.

 

[stabl4life82]

u dont have to buy again..i have restored my phone and had a new phone and i went to the market and it still said purchased for every one of them

 

[xkape]

The only way you are going to lose your apps is if you delete your Google Gmail account. Which I'm not even sure is possible. Never tried.

 

[takeshi]

...or if you change accounts.

 

[diastro]

The only way you are going to lose your apps is if you delete your Google Gmail account. Which I'm not even sure is possible. Never tried.

Certainly it is possible to delete the account and all apps associated with it:
Settings->Accounts->Import->Account settings->Edit->Remove Gmail permanently

http://mail.google.com/support/bin/answer.py?hl=en&answer=8152