Yes paypal is secure, no sewbids can't access it unless your paying through it. I bought on ebay using paypal and made 4 payments on the purchase (contacted seller, he agreed) and he invoiced me, and could only take out what I agreed with my sign in & code, to allow paid out.
One warning...Ebay, NEVER trust even who you are contacting with as the seller. A total of 6 people where scammed for a sewing machine at $1,600. I was new to ebay, and didn't relalize I should have only used paypal to pay, and I sent my money Western Union (thought this had to be secure to, they have to have so much ID to send it...but obviously not to pick it up), it was picked up without ID in Italy, I lost my money, Ebay can't do anything about it, and informed me of the other 5 being scammed. Then on the news, I heard of 2 being scammed for a Harley motorcycle, BIG bucks.
With this sewing machine, I had contacted the seller MANY times with lots of questions, warrenty, etc. He responded, friendly. This was a 100% seller who'd had hundreds of sales, and I researched, this is the type seller your supposed to trust, right? Well, this sellers account had been hacked into, the emails where being intercepted, and he noticed no action on "his sales" so he contacted Ebay, and then from those of us who got scammed complaining, Ebay put 2 & 2 together, to discover this hacking. The "robber" responded to us 'buyers' emails, and stole our money, not even in the USA, the "real" seller was in California, and had nothing to do with sewing machines at all. (I thought I was buying out of Calif too) He ended up having to close his auctions down, and restart from scratch sale #1, and rebuild his reputation under a new name. Felt bad for him, felt stupid and worse for me... NEVER buy outside paypal, it's the only protection you really have.
Oh, and then I recently got a notice by email my paypal account needed updated. I didn't respond, I contacted paypal through my own account, and yes, it did need updated to tie into an account. I talked with a real person by phone, and he told me to open a new account, with debit/visa, ONLY put into that account what I need to make my purchases, and I can choose the paypal to go direct through that account or the visa (which is how I go, as it builds airline miles, I have 8 tickets now on my reg.used card), but still, this account is protected by paypal, by being visa tied, by my bank, and never has more than the money I plan to spend...I transfer it before paying any online purchases..so most of the time it only has $1 in it until I need it again. This man by phone did not ask for any passwords, said they will NEVER request passwords, and he would not even set up my new account info online for me, I had to go into my account and set it up myself. He warned they will NEVER ask your password or account info, it's typed in (becoming dots only) and secure. So far, no problems.