On the LeadBolt opt page you can specify your IMEI number in order to opt out from their service:
The IMEI/MEID is a number, usually unique, to identify GSM, WCDMA, and iDEN mobile phones, as well as some satellite phones. It allows us to identify your device and ensure you are opted out from our services. Importantly, the IMEI/MEID is only used for identifying the device and has no permanent or semi-permanent relation to you as the subscriber protecting your privacy.
Is this safe? Would let me enjoy Android apps without annoying and invasive ads?