Whenever you hear the words “unlimited something” with regard to a hosting plan, this is a clear sign of marketese. No business would be OK with providing you with unlimited disk space, bandwidth, CPU or memory. The hosting providers understand that lots of folks with personal websites will be totally satisfied with the meagre resources they get their hands on in shared plans, and since those sites will never attract a huge amount of traffic, the owners will never use much of the resources, extended to them.
But what if your site starts to grow fast
Other sites can start revving up fast with lots of visitors on a daily basis.
If you continue to hanker to a shared plan you originally purchased, you might be in for a trouble since the hosting provider can actually decide to suspend or even terminate the contract with you. In this case, your site will just stop working.
This is truly a measure of last resort, and most providers will contact you and explain that it’s time to upgrade to a more expensive plan with more “unlimited” resources at your disposal.