Yes, people will buy the Apple watch because Drake wore it. Many fads have taken off because of a celebrity wearer; for instance, twerking became much more popular after Miley Cyrus performed the dance with Robin Thicke. Drooping pants and show-off underwear became widespread due to rappers like Ice-T in the 90's, and even the term 'YOLO' has become pervasive from celebrity useage on social media. Brands like FUBU and objects like shutter shades appeared on celebrities and them went viral in the non-famous population. People love status symbols, and I believe people will flock to be like Drake.
The idea that people will buy what a celebrity has is what has, in my opinion, ingrained the expensive brand name ideals into society. I haven't seen many celebrities wear Old Navy brand clothing, but stick a celebrity into a Gucci ad and everyone wants the new Gucci purse. We depend too much on celebrities for what to buy.
Many people do purchase items because their favorite celebrity owns it, this is similar to how we purchase items our friends have. If people like someone and look up to them as they do with celebrities, then they are more likely to purchase the same things in a way to relate to them and be more like them.
I believe teens are easily influenced, especially by celebrities. I believe teens buying habits are often driven by what their favorite celebrities own or endorse. This is often true of clothing lines that are owned or endorsed by celebrities. I don't think that adults are necessarily influenced to buy items because of celebrities as much as the younger generation.