Does LVM need a partition table ?
- No it doesn't require it (see other answer by Pisacha Srinuan for the link).
Is this a bad idea ?
- In some situations, yes, in other, no.
Explanations (to complete the good answers above that correspond to different use cases):
Nowadays, Linux and LVM are used so widely that many different use cases share these same technologies, but they have very different operational constraints and requirements.
The most common example is: is your LVM disk a storage system A) used by hypervisors to store many virtual machines image files?
Or is it B) for a single, probably virtual, machine ?
In the first case A), you would need to split your LVM disk into smaller portions to reduce the granularity of the volumes space management, and also for your failure recovery risk management. You may also want to use more features of LVM, including RAID redundancy, thin pools, etc... This is best done by splitting your huge disk into partitions of smaller sizes, each of them becoming an LVM PV in your volume group. This way, in case of incident, you may reduce the probability of the incident (with redundancy). And its impact and/or resolution time if you need to resort to physical disk recovery of smaller partitions. How many exactly will depend on your risk tolerance, your service commitments, your availability expectations and design, etc ... A rule of thumb is that reducing the impact and recovery time by a factor of 10 is always welcome, and 10 is still a manageable number for partitions.
Another reason is LVM Metadata stored on each PV. LVM does store its metadata in several locations on each PV, according to Red Hat LVM docs. If you use a raw device instead of a partition, the creation of a partition table at some time, like during a data recovery attempt, would overlap with and damage your LVM metadata and render you data unusable, or much more difficult to recover. This data loss would not happen on a disk with a pre-existing partition table.
In the case B), a single system might benefit from the simplicity of a PV without partition table, as the recovery process might be ensured by the hypervisor layer backup system, if it is a virtual server. But you need to make sure of it before to decide to go for this simplicity.