Feet are the largest fetish object out of all paraphilia. As a poster noted above about 5% of the male population hold an attraction to feet or one of the many feet related sub-philia.
For a quick class on the grouping it breaks down into several distinct sub groupings.
1) Observers. The largest faction. These people respond to feet in an almost one-to-one correspondence to the culturally accepted body parts to lust for (Breasts, Vagina, Ass, Legs) They get the same sort of arousal response that the 'vanilla' people get from the other body parts. And like a person might be into a specific size and shape of breast, nipple type etc, this foot grouping will fragment over toe length, foot shape, arch size etc. They will get very very idiosyncratic about what makes for an attractive foot to them, and when they see one that hits all the buttons they will focus deeply.
Co-philia like nylon, shoes, socks, dirty feet, toe nail polish color etc all also fall under the same grouping of Observers, just with the added aspect of a secondary philia mapped over it.
2) Manipulators. This group wants to interact with the foot. This includes the worshipers, toe suckers, ticklers, foot job fans, massagers. These folks see the foot as an agent to act or be acted upon. Their arousal comes out of the results of that interaction. Again this can be mapped against traditional behaviors involving the traditional sex areas, and seen in those contexts. A person who gets off on sucking toes, responds much like one who loves to suck nipples.
3) Psychological. This group views the foot as an object that directly links to power exchange and Dominance/Submisison. These folks get off on the teasing with feet (Dangling, slipping shoes on and off, footsie sort of games) Direct actions like trampling, or forced worship and so forth. These people's interest in feet is tied to their greater D/s desires, and feet are the 'key' that opens that lock in their arousal psychology.
A cam-modle will mostly deal with the Observers, as the other groups tend to need a two people to functionally work. Regardless of what you, the model may think of your feet, there will be people who think they are the hottest feet ever. Once again, you might have had similar concerns with some other aspect of your body and found that there were viewers who loved you all the more for it.
It is of course a form of objectification of a body part, and carries the same feelings as if your traditional sex body areas were being singled out and focused upon, made to feel more odd by the fact that the attention is non-cultural normative. A lot of people have issues with the foot fetish when they realize that there might be a lot of people getting off on their feet without their knowledge at any time in their normal day to day life. A reaction to the voyeuristic element of the philia.
Hope this helps with the folks who were curious about the philia.