i love Lookout.
1. it can find your phone if it's lost or stolen - even if your battery dies.
2. it's lightweight - it uses very little battery and resources.
3. the malware detector works. i tested it by purposely installing "SMS Replicator" and it caught it on my phone after a scan.
4. i trust them - they are a reputable AMERICAN company based in the U.S. it's not about patriotism. it's that i trust an American company more than i trust a foreign company (like one located in the Czech Republic or Russia) with my data security.
5. it's FREE.
IMO - install it.