I'm starting a video sharing site, not sure how much traffic I will be able to get, so will I feel comfortable on a shared plan with FFMPeg installed? Considering HostV.com as a host, can you suggest other options?

I think the majority of hosts offer video and audio streaming feature on their plans, iа this is what you are after check Hostgator.com and Serverpoint.com shared plans, if your site becomes popular, you could upgrade to a VPS plan within the same company.

If you are going to use video services from HostV.com, you have to know that this comapny offers a lot of video sharing scripts too. MOre info about that you may find in their blog.

I think that you need to think about dedicated server at all.
I would recommend you hqhost.net as one of most stable one and not expensive provider.

@ OP, if you plan to use video services, HostV.com will be good for that because this company specializes in FFMpeg and Red5 services.

HostV.com is the right place to use FFMpeg module from. Their double RAM and many other features that are included into their plans are clients friendly and can be used in a quality way.

I think that for YouTube site you will neeed either web server or streaming media server to be installed on a dedicated server.
To make things less costlier, I suggest getting a low-end dedicated server and installind a web server for streaming on it.
You may find low-end dedicated server offers among ahosting.biz offers.