Depends on how paranoid about security you are. They are not critically important apps.

BTW there are very good alternative security apps which are not resource hogs.
I personally use Avast! mobile security, it's a free app and has one of the best theft securities i have seen, it's a complete security package and best part is that it's not a resource hog. But to be able to enjoy all of it's benefits you need a rooted phone though it's not required to be rooted for most of the options.

 

I would recommend AVG and Android Lost.

 

Forbidden 403, to use anti theft on avast do i need to root my phone? And what exactly does root the phone means ?
Thanks

 

@Pawlu00
No you don't need root access to use that app, but there are certain advanced features in the app which shall be available only if you have root access.
For example, if you have root you can set it up in such a way that even on formatting the phone the thief won't get rid of the app and you can track it.
But most of the features shall work even without root.

For more details regarding rooting refer to the following guide.
Samsung Galaxy S2 (International) - All Things Root Guide

 

@ forbidden 403
thanks for your previous comment. Can you please guide me in activating anti theft, because every time i try to do it, it says "setup will need to access non Android-Market download locations. Please enable installation of non-market apps in your system settings" and advises to open my settings and got lost :S. Currently using ICS
Thanks

 

i do use the avast security..its really cool app..for most of the features u don't need need to be rooted..it even sends messages from the thefts phone to ur trusted numbers (believe me i tripped check.) if it prompted u to do that the go to settings > applications > then u thick unknown source..i am not sure it asked me for that when i installed mine..make sure u are not downloading the pirated version.

 

@Pawlu00 dapsonddroid gave the gave the answer
go to settings -> security -> (scroll down) make sure "Unknown sources" is ticked
here is a screenshot of the same

 

thanks alot

 

where is my thank u @Pawluoo (joking) ..glad i could be of help

 

There you go, Thanks on my behalf too